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IC 9235 



BUREAU OF MINES c36 y 
INFORMATION CIRCULAR/1990 



-/ 



^'■' 



Reducing Back Injuries in 
Low-Coal Mines: Redesign 
of Materials-Handling Tasks 



By Sean Gallagher, Thomas G. Bobick, 
and Richard L. linger 




3 

Q 



•£NT op . 



80 

* YEARS g 

***U OF ^ 



1 
o 



BUREAU OF MINES 
1910-1990 

THE MINERALS SOURCE 



Mission: Asthe Nation's principal conservation 
agency, the Department of the Interior has respon- 
sibility for most of our nationally-owned public 
lands and natural and cultural resources. This 
includes fostering wise use of our land and water 
resources, protecting our fish and wildlife, pre- 
serving the environmental and cultural values of 
our national parks and historical places, and pro- 
viding for the enjoyment of life through outdoor 
recreation. The Department assesses our energy 
and mineral resources and works to assure that 
their development is in the best interests of all 
our people. The Department also promotes the 
goals of the Take Pride in America campaign by 
encouraging stewardship and citizen responsibil- 
ity for the public lands and promoting citizen par- 
ticipation in their care. The Department also has 
a major responsibility for American Indian reser- 
vation communities and for people who live in 
Island Territories under U.S. Administration. 



Information Circular 9235 



Reducing Back Injuries in 
Low-Coal Mines: Redesign 
of Materials-Handling Tasks 



By Sean Gallagher, Thomas G. Bobick, 
and Richard L. Unger 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Manuel Lujan, Jr., Secretary 



BUREAU OF MINES 
T S Ary, Director 






Library of Congress Cataloging in Publication Data: 



Gallagher, Sean. 

Reducing back injuries in low-coal mines: resdesign of materials-handling tasks 
/ by Sean Gallagher, Thomas G. Bobick, and Richard L. Unger. 

p. cm. - (Bureau of Mines information circular 9235) 

Bibliography: p. 33 

Supt. of Docs, no.: I 28.27:9235. 

1. Mine haulage. 2. Coal mines and mining. 3. Back-Wounds and injuries. 
4. Lifting and carrying. I. Bobick, T. G. II. Unger, Richard L. III. Title. 
IV. Series: Information circular (United States. Bureau of Mines); 9235. 

TN295.U4- [TN331] 622 s-dc20 [622'.8] 89-600172 

CIP 



CONTENTS 

Page 

Abstract 1 

Introduction 2 

Prevention of back injuries in low-coal mines 2 

National Institute for Occupational Safety and Health (NIOSH) Work Practices Guide for Manual Lifting 2 

Model for redesign of underground materials-handling tasks 3 

Chapter 1. -Identifying materials-handling problems 3 

Review of accident statistics 3 

Company accident records 3 

Mine Safety and Health Administration (MSHA) data base 5 

Task analysis 5 

Equipment needed for task analysis 5 

Performing the analysis 6 

Task analysis example 7 

Summary 8 

Chapter 2.-Eliminating and mechanizing materials-handling tasks 8 

Elimination of materials-handling tasks 8 

Using task-specific mechanical-assist devices 9 

Heavy-component lift-transport 10 

Beam-raising vehicle 10 

Scoop-mounted lift boom 10 

Machine-mounted swivel crane 12 

Mine mud cart 12 

Container-workstation vehicle 12 

Systems approach to materials handling 12 

Summary 16 

Chapter 3.-Matching job demands to worker capabilities 16 

Anatomy of the back and causes of low-back pain 17 

Methods of determining lifting capacity 18 

Biomechanical approach 18 

Physiological approach 19 

Psychophysical approach 20 

Comparison of the approaches 20 

Bureau of Mines lifting capacity studies 20 

Lifting capacity of underground miners 20 

Physiological stress of lifting in restricted postures 21 

Biomechanics of lifting in restricted postures 21 

Redesigning manual lifting tasks to miner's physical capabilities 22 

Maximum recommended weights of lift 22 

Redesign of materials 22 

Handling heavy weights 23 

Reducing lifting frequency 23 

Need for more frequent rest breaks when kneeling 23 

Stresses of lifting when stooped 23 

Modification of work environment 24 

Lifting technique 24 

Summary 25 

Chapter 4-Examples of alternative redesign strategies 25 

Elimination of materials-handling tasks 25 

Redesigning materials-handling tasks using mechanical-assist devices 26 

Redesigning lifting tasks to fit worker lifting capacity 26 

Worker selection and training procedures 26 

Worker selection 26 

Worker training 27 

Implementation and evaluation of redesign strategy 27 

Summary ■ . 27 



CONTENTS-Continued 

Page 

Chapter 5.-Management policy and control of back injury costs 27 

Promotion of physical fitness 27 

Back fitness program 28 

Stretching 28 

Strength conditioning 30 

Back care at home 30 

Control of costs once a back injury has occurred 30 

Positive acceptance of low-back pain by management 30 

Early intervention 30 

Followup and communication 30 

Early return-to-work programs 31 

Summary 31 

Chapter 6— Summary of recommendations 31 

References 33 

ILLUSTRATIONS 

1. A model for redesigning materials-handling tasks 3 

2. Method for identifying hazardous materials-handling tasks 4 

3. Bureau researcher performing underground task analysis 5 

4. Concrete block handling 

5. Comparison of methods for transporting concrete blocks at two mines 8 

6. Cable ramps eliminate manual lifting 9 

7. Heavy-component lift-transport 11 

8. Beam-raising vehicle 11 

9. Scoop-mounted lift boom 12 

10. Installation of machine-mounted swivel crane 13 

11. Machine-mounted swivel crane in use underground 13 

12. Mine mud cart 14 

13. Container-workstation vehicle 14 

14. Interchange of containers on container-workstation vehicle 15 

15. Vertebral column 17 

16. Intervertebral disk " 17 

17. Example of biomechanical stresses 18 

18. Analyzing subject's expired air 19 

19. Underground miners performing lifting capacity tests at Bureau of Mines Ergonomics Laboratory 21 

20. Miners have higher lifting capacity when stooped 23 

21. Miners may fatigue more quickly when kneeling 23 

22. Stooped posture may be less tolerable for some miners 23 

23. Twisting during a lift 24 

24. Miners assisting one another with heavy load 25 

25. Prone pushup and back stretch 29 

26. Abdominal strengthening exercises 29 

27. Strengthening back muscles 29 

TABLES 

1. Estimated cost of back injuries in coal mining industry during the years 1981-86 2 

2. Results of accident analysis examining occupations experiencing highest incidence of back injuries 4 

3. Results of accident analysis relating to activities causing back injuries at an underground coal mine .... 4 

4. Hazardous mine and equipment maintenance tasks, 1980 data 10 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 


ft 


foot 






lb 


pound 


h 


hour 






L/min 


liter per minute 


in 


inch 






min 


minute 


kcal/min 


kilocalorie 


per 


minute 


pet 


percent 



REDUCING BACK INJURIES IN LOW-COAL MINES: REDESIGN 
OF MATERIALS-HANDLING TASKS 



By Sean Gallagher, 1 Thomas G. Bobick, 2 and Richard L. linger 3 



ABSTRACT 

This report describes research by the Bureau of Mines on alternative materials-handling strategies 
for reducing the costs and incidence of back injuries in low-seam coal mines. Strategies recommended 
for redesigning materials-handling tasks include elimination of tasks, mechanization of tasks, and 
matching lifting tasks to the physical capabilities of underground miners. The report also discusses other 
methods that can be used by management to reduce the costs associated with back injuries. 



1 Research physiologist. 

2 Mining engineer (now with National Institute for Occupational Safety and Health, Morgantown, WV). 

3 Civil engineer. 

Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 



INTRODUCTION 



Low-back pain is the most common cause of occupa- 
tional disability in the U.S. underground coal m inin g in- 
dustry. In fact, approximately 25 pet of injuries in under- 
ground coal mines involve trauma to the back. These 
injuries represent the leading cause of lost workdays in 
underground mines and typically account for 30 to 40 pet 
of worker compensation payments made by the industry. 
A large portion of these injuries (estimated at about 
35 pet) are related to manual handling of supplies, parts, 
and equipment (i). 4 

Table 1 illustrates the costs of coal mining back injuries 
from 1981 through 1986. These data are based on accident 
records contained in the U.S. Mine Safety and Health 
Administration (MSHA) data base, analyzed using the 
Bureau of Mines Accident Cost Indicator Model (ACIM). 
According to ACIM, the estimated cost of back injuries in 
coal mining for 1981-86 was over $100 million. This es- 
timate should be viewed as a conservative figure because, 
in addition to the costs estimated in table 1, there may be 
other so-called hidden costs, such as costs of training new 
workers, administrative costs, legal fees, and so forth, that 
may drive the total cost of these injuries still higher. The 
data presented here clearly demonstrate that traditional 
methods of preventing back injuries (for example, worker 
training) have had limited success, and that new and in- 
novative approaches of controlling the problem of back 
injuries in the mining industry are needed. 

Table 1 .-Estimated cost of back injuries (million dollars) 
in coal mining industry during the years 1981-86 



Year 



Cost to- 



Total cost 





Industry 


Family 


Public 




1981 . . 


12.5 


5.7 


2.1 


20.3 


1982 . . 


12.6 


5.1 


.6 


18.3 


1983 . . 


8.7 


3.9 


.6" 


13.2 


1984 . . 


9.9 


4.4 


.6 


14.9 


1985 . . 


14.6 


5.9 


3.0 


23.5 


1986 . . 


10.1 


6.2 


.4 


16.7 



Source: MSHA data base, using Bureau's ACIM. 

PREVENTION OF BACK INJURIES 
IN LOW-COAL MINES 

The underground low-coal mining environment presents 
some unique barriers to preventing back injuries (2). The 
restricted roof height of low-coal mines (seam thickness of 
less than or equal to 48 in) forces miners to adopt stressful 
working postures during manual materials-handling activ- 
ities. Miners generally stoop and kneel when lifting in 
low-seam mines. Both postures cause a considerable 
amount of stress on the spine and may account for the 
high incidence of low-back pain in the coal mining indus- 
try. The confined workspace of low-seam mines makes the 
use of certain types of mechanical-assist devices more 



4 Italic numbers in parentheses refer to items in the list of references 
at the end of this report. 



difficult. In addition, the problems of poor illumination 
and slippery work conditions may compound the problems 
associated with manual materials-handling underground. 
The traditional approach to reducing the risk of back 
injuries has been to train miners to cope with the existing 
work conditions. Unfortunately, this method is very limit- 
ed in terms of effectiveness (3). In recent years, a much 
more constructive method of preventing back injuries has 
evolved, called ergonomic redesign of the workplace. It 
has dramatically reduced both the incidence and cost 
associated with low-back pain in many industries. Simply 
stated, ergonomics is a science that strives to match the 
demands of a job to the worker's capability to perform the 
job. Too often, workers must perform tasks that exceed 
their capabilities. When this happens, the risk of injury to 
the worker is great. Matching the job demand to the 
worker's capability reduces the risk of injury. Workers 
may also interact more effectively with the working envi- 
ronment. In addition, certain modifications in the way a 
job is performed (and often these can be quite simple) can 
significantly lessen a worker's chances of sustaining an 
injury. 

NATIONAL INSTITUTE FOR OCCUPATIONAL 

SAFETY AND HEALTH (NIOSH) WORK 
PRACTICES GUIDE FOR MANUAL LIFTING 

In 1981, the National Institute for Occupational Safety 
and Health (NIOSH) developed a "Work Practices Guide 
for Manual Lifting" (4). The work practices guide sum- 
marizes a vast amount of research related to the biome- 
chanical, physiological, and psychophysical stresses associ- 
ated with manual lifting. This Guide presents quantitative 
recommendations for establishing safe load limits based 
upon factors such as the size of the load, the frequency of 
lifting, and the location of the load at the start and end of 
the lift. The Guide also presents recommendations re- 
garding worker strength capabilities, worker training, and 
physical fitness, as well as specific engineering guidelines 
for the design of workplaces. The mine safety and health 
professional who is serious about reducing injuries due to 
manual materials-handling is encouraged to study this 
document. 

Unfortunately, the recommendations contained in the 
NIOSH Guide are somewhat limited in terms of applica- 
bility to the underground mining environment (particularly 
low-seam mines). The lifting limits in the Guide assume 
the worker is lifting in an unrestricted working posture, 
lifting directly in front of the body without twisting. Addi- 
tionally, the limits apply only to lifting situations having 
good couplings (for example, handles on boxes and dry 
floor surfaces). Unfortunately, many lifting tasks per- 
formed in low-seam coal mines violate many (if not all) 
of these assumptions. For this reason, the Bureau has 
undertaken to examine the unique problems associated 
with manual materials-handling in underground mines and 
to develop recommendations for ergonomic redesign of 



lifting tasks in the restricted low-seam coal mining envi- 
ronment. This work was done in support of the Bureau's 
program to enhance the health and safety of mine workers. 

MODEL FOR REDESIGN OF UNDERGROUND 
MATERIALS-HANDLING TASKS 

Figure 1 presents a model that can assist in the redesign 
of materials-handling tasks in low-seam coal mines. This 
model outlines the sequence of steps that should be fol- 
lowed (and questions that should be asked) when deter- 
mining alternative materials-handling strategies in low- 
seam coal mines. This figure, which summarizes the 
materials-handling redesign strategies advocated by the 
Bureau, is referred to throughout this report. 

The ensuing chapters discuss the various components of 
the task redesign procedure. Chapter 1 of this report 
describes methods by which a mine's current supply- 
handling system can be analyzed both to identify favorable 
aspects of prevailing procedures and, more importantly, to 
detect materials-handling problem areas. The two most 
effective redesign strategies, elimination of unnecessary 
manual lifting and mechanization of materials-handling 
tasks, are discussed in chapter 2. Chapter 3 presents re- 
sults of Bureau research demonstrating how lifting capacity 
is reduced in the restricted postures often used in low- 
seam mines and discusses redesigning underground manual 
lifting tasks according to the physical capabilities of the 
worker. Examples of redesign techniques are contained in 



Examine supply- 
handling system 



Identify materials- 
handling problems 



Consider 
alternative 
strategies 



X 



Evaluate 
changes 



Implement 
solution 




Can task be 
eliminated ? 



Can mechanical 
assist be used ? 



Can 
task be redesigned 
to fit worker 
lifting capacity? 

| No 



Use worker 

selection and 

training procedures 



Figure 1 .-A model for redesigning materials-handling tasks. 



chapter 4. The role of management in reducing disability 
due to back injuries is contained in chapter 5. Finally, a 
review of recommended practices for handling materials in 
low-seam coal mines is presented in chapter 6. Proper 
application of the redesign techniques contained in this 
report may be very helpful in controlling the costs of back 
injuries experienced in low-seam mines. 



CHAPTER 1. -IDENTIFYING MATERIALS-HANDLING PROBLEMS 



The techniques for handling items in the underground 
workplace, whether manually or mechanically, can vary 
extensively depending on the environmental factors of the 
mine, available equipment to assist in moving items, and 
current management practices. Unfortunately, many 
supplies and heavy equipment components are still rou- 
tinely handled manually in underground coal mines. Iden- 
tifying problems or bottlenecks in existing materials- 
handling systems can lead to a reduction in the number of 
times that supplies have to be handled manually (through 
the redesign techniques discussed in later chapters), and 
this process should ultimately diminish the chance that 
workers will experience a low-back injury (or any other 
musculoskeletal injury). 

Important aspects of analyzing the current supply- 
handling system include reviewing past accident statistics, 
observing the problem jobs or areas in the workplace, 
interviewing the involved workers, and considering alter- 
native procedures to the existing materials-handling system. 



Figure 2 provides a flowchart to help identify specific 
materials-handling problems. The various components of 
this flowchart are discussed throughout this chapter. 

REVIEW OF ACCIDENT STATISTICS 

Company Accident Records 

The goal of the accident analysis is to identify activities 
that lead to injuries so that such injuries can be prevented 
in the future. An analysis of past accident records will 
help pinpoint the occupations and the activities that have 
contributed to both lost-time and non-lost-time accidents. 
A comprehensive analysis of the accident reports should be 
performed to identify the physical conditions, body pos- 
tures, and work activities of injured workers at the time 
of injury. The occupations or materials-handling activities 
associated with high injury rates will, of course, be the 
prime candidates for job redesign. 



Review 


accident 




Compile 
statistics 




Rank-order problem 

occupations and 

activities 




Observe problem 
areas underground 


reports 


























i 


i 
















Use still photography 




Ask probing questions 

about the present 

materials-handling 

system 




Encourage feedback 

from the involved 

workers 




Consider alternative 


ana/or viae 
detailed 


analysis 








strategies 



Figure 2.-Method for identifying hazardous materials-handling tasks. 



The compilation of accident statistics and the estimate 
of injury potential can be used to rank-order the occupa- 
tions and the job duties that have caused problems when 
materials are handled or moved. An example of an acci- 
dent analysis, contained in tables 2 and 3, has identified 
the occupations and activities associated with back injuries 
at an underground coal mine. According to the accident 
data presented in table 2, the three jobs where most back 
injuries occurred were general laborer, maintenance me- 
chanic, and roof bolt operator. These jobs should be 
carefully examined through a task analysis so that the 
materials-handling hazards associated with them can be 
identified. Once the hazardous activities of these jobs have 
been recognized, alternative materials-handling strategies 
can be developed. 



Table 2.-Results of accident analysis examining 

occupations experiencing highest incidence 

of back injuries 



Table 3. -Results of accident analysis relating 

to activities causing back injuries 

at an underground coal mine 



Occupation 



General laborer 

Maintenance mechanic 

Roof bolter operator 

Shuttle car operator 

Conveyor belt operator 

Supervisor 

Electrician 

Continuous miner operator .... 
Other 



pcf of all 
back injuries 

27 

19 

15 

8 

7 
4 
4 
4 
12 



Activity causing injury 



Materials handling 

Equipment maintenance . . 

Roof bolting 

Operating shuttle car 

Using prybar 

Operating continuous miner 

Shovelling 

Other 



pet of all 
back injuries 

42 
18 
10 

5 

4 

4 

3 
14 



The analysis of the activities that were responsible for 
the back injuries (table 3) indicates that materials-handling 
activities were the leading cause of back injuries, followed 
by equipment maintenance and roof bolting. These results 
are not surprising, because all of these activities require 
considerable heavy lifting and other physical exertion. 
Obviously, it is necessary to develop safer and more effi- 
cient methods of performing these hazardous tasks. 

Another important aspect of the accident analysis is 
interviewing injured workers to gather more information 
about the causative factors of the injury than what is in- 
cluded in the usually brief accident description. During 
this dialogue, workers should be encouraged to suggest 
ideas they have for redesigning the workplace or changing 
the standard work procedure. Getting the employees to 
provide feedback promotes worker involvement in elimi- 
nating potential hazards. 



Mine Safety and Health Administration 
(MSHA) Data Base 

If the mine is relatively new and does not have 3 or 
4 years of accident statistics to review, the MSHA data 
base of accidents can be utilized. This data base provides 
the total number of lost-time accidents, parts of body 
injured, causes of accidents, and activities at the time the 
injuries occurred, for all U.S. mines that reported injuries 
on the "Mine Accident, Injury and Illness Report" (MSHA 
form 7000-1). Thus, these data can be used to focus at- 
tention on jobs and activities that have contributed to lost- 
time accidents in other U.S. mines. This compiled infor- 
mation is available from MSHA in its ongoing series of 
reports entitled "Injury Experience in Coal Mining" (5). 

TASK ANALYSIS 

After the accident statistics are compiled and analyzed, 
problem areas in the mine should be visited to determine 
the hazardous conditions associated with performing spe- 
cific mining jobs. A task or job analysis should be per- 
formed to identify the various factors that characterize the 
materials-handling situation. Such an analysis usually 
consists of a detailed listing of the job activities in a sys- 
tematic order, generally in the sequence in which they 
occur in the job (6). The intent of the task analysis is to 
characterize the hazardous components of the job and the 
corresponding bodily actions or postures that are required 
to complete that job. The primary objective of the task 
analysis is to identify ways to reduce the number of times 
that items are manually handled. The more often supplies 
are manually handled, the greater the potential that a 
worker will experience a back injury. In addition, an 
increase in breakage and waste of materials is likely the 
more often these supplies are handled. 

Equipment Needed for Task Analysis 

Various types of equipment can be utilized to document 
the occupational demands and materials-handling activities 
present in the underground mining environment. Video- 
tape, still photography, portable tape recorders, and taking 
notes are some of the best methods to document the entire 
job sequence. Videotape is the preferred recording system 
for a task analysis, because the analyst can watch the job 
being performed in "real" time. Videotape can also be 
reviewed and analyzed as many times as needed to provide 
information about the hazardous activities of that job. In 
addition, most videotape units allow the analyst to take 
verbal notes while videotaping. Figure 3 shows a Bureau 
researcher using videotape equipment while performing a 
task analysis underground that documented the movement 
of supplies and equipment parts. 



Mines that may consider purchasing a videotape re- 
cording system to record activities underground should 
realize that additional lighting may be required for under- 
ground videotaping. However, low-light-level videotape 
sytems can also be purchased. Although they operate 
quite adequately close to the subject (5 to 8 ft), some extra 
lighting is usually required if the subject is 15 or 20 ft from 
the camera. An important consideration is the permissi- 
bility of the video system and the auxiliary lighting. Com- 
mercially available photographic products can be used 
underground in fresh air but, of course, cannot be taken 
beyond the last open crosscut. To determine the permis- 
sibility of equipment, the items in question need to be 
tested by MSHA's Approval and Certification Center, 
Triadelphia, WV. To videotape tasks such as installing 
temporary roof supports would require using a permissible 
system or, alternatively, posing those tasks for videotaping 
in another part of the mine that is in fresh air. A flash 
that is typically used with a still camera is nonpermissible. 
A permissible flash, however, is commercially available. 
This flash unit permits still photos to be collected of tasks 
that are conducted in the face area of the mining section. 
Those mines that do not have the resources to purchase a 
videotape recording system can use still photography and 
a handheld tape recorder to document the activities of a 
particular job. The tape recorder is a good way to compile 
notes and observations quickly and easily about the phys- 
ical layout and environmental conditions of the sections 
visited during the task analysis. 




Figure 3.-Bureau researcher performing underground task 
analysis. 



Performing the Analysis 

There are two primary approaches that can be used in 
a task analysis of the materials-handling problems in a 
mine. One approach is to examine the flow of supplies 
from the point of delivery to the point of end use. For 
example, one might record the current methods of trans- 
porting concrete blocks from the point of delivery on the 
surface to the actual building of the ventilation stopping 
underground. The task analysis videotape should doc- 
ument each step in the movement of these supplies from 
surface storage to end-use locations underground. The 
same procedure should be followed for all manner of 
supply items. The information collected in the task anal- 
ysis can subsequently be analyzed to determine ways in 
which the supply-handling system can be made safer and 
more efficient. 

The other approach is to examine the hazards associ- 
ated with specific occupations. For example, if an accident 
analysis has shown that mechanics experience a significant 
number of lost-time injuries, the examiner would want to 
follow a mechanic throughout the working day to video- 
tape the tasks required by the job. The analyst would want 
to distinguish the most hazardous tasks of this job and 
evaluate alternative methods (such as using mechanical- 
assist devices to aid in lifting tasks) that could reduce the 
hazards. 

Analysis of Videotape and Photographic Data 

As mentioned previously, one benefit of documenting 
tasks on videotape is that it can be reviewed as many times 
as necessary to determine an appropriate materials- 
handling solutions for hazardous tasks. Some experts in 
the field of task analysis feel that repeated viewing of a 
videotape of a particular task is very helpful in developing 
creative solutions as to how the job may be more safely or 
efficiently performed. It is often helpful to have two or 
more persons review the videotape so that the analysts can 
brainstorm methods for improving the current materials- 
handling methods. 

As part of the process to eliminate or reduce manual 
handling of supplies and parts, the analyst should question 
all aspects of the supply-handling system. Consider an 
example: Suppose the task analysis videotape shows that 
considerable disorganization exists at the surface supply 
yard at a mine. What is the scope of the problem? Is it 
limited to the supply yard itself? Is it caused by inad- 
equate on-site storage facilities, or is it caused by poor 
materials-handling practices? Could the problem be the 
way the materials are received from the suppliers? Can 
the schedule for delivery of supplies and equipment be 
more regimented, instead of being dependent on the sup- 
plier's schedule? Can the supplies be received in a dif- 
ferent configuration (already on a pallet or banded 



together, instead of loose) to promote mechanical handling 
of materials? 

The problem definition should contain quantitative 
information whenever possible. If there is a designated 
area for underground storage of parts or supplies, what are 
the dimensions of each storage compartment or area? 
How far away from the active face is it? How many dif- 
ferent parts or supply items are stored there? How have 
materials been organized in the storage areas? Are the 
supplies organized before they are delivered to the pro- 
duction sections? 

Generalized checklists, which help identify hazardous 
conditions and activities of typical materials-handling jobs, 
have been developed for the manufacturing industries. 
They are general enough so they can be used or easily 
modified for use in the underground mining industry. The 
checklist that follows can be a starting point to identify 
materials-handling problems in the underground 
workplace. 

1. Crowded operating conditions. 

2. Cluttered entries and supply areas. 

3. Poor housekeeping. 

4. Delays or backtracking in flow of supplies. 

5. Obstacles in flow of materials. 

6. Manual handling of loads weighing more than 45 lb. 

7. Two-worker lifting jobs attempted by a single 
employee. 

8. Excessive temporary storage. 

9. Excessive time spent retrieving stored parts or 
supplies. 

10. Excessive manual loading and unloading. 

11. Single items handled instead of unit loads. 

12. Excessive breakage of supplies or damaged parts. 

13. Not utilizing materials-handling equipment when 
appropriate. 

Although the checklist should not be relied upon exclu- 
sively to identify problems with the system, it may help to 
spot signs and symptoms that are associated with poor 
materials-handling practices. 

Interviewing Workers 

As with the accident analysis, an important aspect of the 
task analysis process is encouraging the workers to provide 
their observations and comments regarding any of the 
potentially hazardous areas or activities. The workers may 
have already tried to incorporate some sort of change to 
the workplace or to the work method to alleviate the haz- 
ardous condition or awkward posture. Getting feedback 
from the workers regarding their suggested modifications 
sometimes provides the analyst with the beginnings of a 
permanent solution for those situations. 



Task Analysis Example 

A comparison of two task analyses performed at un- 
derground coal mines by the Bureau can help to demon- 
strate the usefulness of documenting the current methods 
of supply-handling at the minesite. The first mining oper- 
ation received its concrete ventilation blocks from the 
supplier in a loose configuration. The individual blocks 
were stacked onto the storage pile by the supplier. Sim- 
ilarly, the supply workers had to manually load the supply 
car with concrete blocks at the beginning of each shift. 
This required that each block be handled twice; the first 
time, workers removed a block from the storage pile and 
set it upright on the supply car, and the second time, they 
stacked the block neatly on its side so the load would clear 
a low spot along the main haulageway (fig. 44). The 
blocks were handled a third time when they were unloaded 
in an underground storage area. When they were needed 
at a work location, the blocks were manually loaded (a 
fourth time) onto the top of a shuttle car or into the buck- 
et of a scoop. If the scoop was used, the blocks could be 
mechanically unloaded with the hydraulically powered 
pusher plate. If a shuttle car was used, the blocks were 
manually unloaded at the work location. Thus, for this 
mine each concrete block was manually lifted a total of 
four or five times from when it left the surface storage 
area until it reached the location underground where the 
ventilation stopping was to be built. 

In contrast, the second mining operation received its 
blocks banded together as a unit of 84 blocks. A forklift 
was used to load the units onto the supply car on the 
surface (fig. 4B). The supply car was then left at the op- 
erating section. When the blocks were needed, a chain 
was wrapped around the banded blocks and the pusher 
plate of a scoop was used to pull the unit load off the 
supply car. The scoop then delivered the blocks to the 
location where the ventilation stopping was to be con- 
structed. This procedure eliminated all manual lifts except 
for the final placement of the blocks. 

A typical ventilation stopping, which is 20 ft wide and 
44 in high, requires 6 rows of block with 15 blocks to a 
row, or a total of 90 blocks. Compared with procedures 
used at the first workplace, up to 450 manual lifts have 
been eliminated per stopping by the mechanization pro- 
cedure employed by at the second workplace and the risk 
of worker injury has been substantially reduced. 

Figure 5 shows flowcharts, developed from the task 
analyses at these two mines, of the movement of the blocks 
from the surface storage area to their end-use location. 
Three modes of movement are shown. Manual transfer 
occurs when the supplies are moved manually with sup- 
port, such as when a miner manually drags a block to the 
edge of the supply car. Manual transport is unsupported 
movement of the supplies, such as lifting a block from the 
surface storage pile and stacking it on the supply car, or 




■*~ 



/.*»._ 



f 






mm* 



*r* , 



r* 




Figure 4.-Concrete block handling. A, Loading blocks at 
mine A required hundreds of lifts; B, mine B received blocks 
banded together so that they could be loaded mechanically. 



lifting a block from the supply car and stacking it on the 
underground storage pile. Mechanical transfer or trans- 
port includes any handling of supplies or material con- 
ducted entirely by mechanical means. An example of 
mechanical transfer would be using a chain and the pusher 
plate of a scoop to drag or push a unit load of blocks off 
the supply car; an example of a mechanical transport is 
using a scoop to move the blocks to the work area where 
the ventilation stopping is to be built. 

The flowchart of the concrete block movement at mine 
A indicates that the blocks are being handled unnecessarily 
many times before reaching their final location. The flow- 
chart of the same activity at mine B shows that all manual 
handling has been eliminated, except for final placement 
of the blocks. This sort of flowchart can be a very useful 
tool for identifying problems with the current supply- 
handling system and tasks that can be redesigned to make 
the system safer and more efficient. 




Positioned for 
removol from 
surface storage 



Transported from 
surface storage 
to supply car 



TYPICAL MOVEMENT OF CONCRETE BLOCKS IN MINE A 



KEY 
□ Manual transfer 
O Manual transport 

<£> Mechanical transfer 
or transport 




Banded units 
loaded on supply 
car with forklift 



Unit dragged off 

supply car with chain 

into scoop bucket 



Unit unloaded 

in crosscut with 

pusher plate 



Unloaded with 

pusher plate 

of scoop 



TYPICAL MOVEMENT OF CONCRETE BLOCKS IN MINE B 



Figure 5.-Comparlson of methods for transporting concrete blocks at two mines. 



SUMMARY 

This chapter has discussed the importance of identifying 
materials-handling problems specific to each workplace as 
the initial step in reducing injuries caused by handling 
materials. A review of past accident reports is necessary 
to identify problem areas. High-risk jobs and activities 
should be observed while they are performed. A task 
analysis can define the components of the job and identify 
hazardous procedures. Use of a videotape recorder, still 
photography, a handheld tape recorder, and the analyst's 
own notes will assist with a detailed analysis of job com- 
ponents. When the materials-handling system Is examined, 



every aspect should be critically questioned. Just because 
a particular technique or method of operation has tradi- 
tionally been used in a mine's supply-handling system does 
not mean that it is the safest or most efficient way to ac- 
complish the movement of supplies and equipment. 
Equally important is the need to encourage the workers to 
provide their observations and comments regarding the 
supply-handling system. By considering input from all of 
these areas, alternative strategies can be developed and 
implemented. Subsequent chapters discuss methods of 
redesigning materials-handling tasks to reduce the risk of 
injury to the worker. 



CHAPTER 2.-ELIMINATING AND MECHANIZING MATERIALS-HANDLING TASKS 



Once a task analysis has identified potentially hazardous 
materials-handling problems, alternative strategies should 
be developed and implemented. As seen in figure 1, the 
two most desirable redesign strategies are elimination of 
the materials-handling task and the development and use 
of mechanical-assist devices to perform the task. This 
chapter presents ideas for reducing the amount of manual 
materials handling in underground coal mines using these 
two redesign strategies. Given that every mine is in some 
way unique, the specific examples may not work at every 
mine. However, the concepts presented, when correctly 
applied, are valid for most (if not all) mining operations. 



ELIMINATION OF MATERIALS- 
HANDLING TASKS 

Elimination of hazardous materials-handling tasks (es- 
pecially manual tasks) is the best way to avoid injuries. 
Eliminating, reducing, or combining movements of supplies 
is often accomplished through the use of mechanical de- 
vices; however, materials-handling tasks can also be elim- 
inated through better organization and planning of the 
supply-handling system. 



The following are examples of the kinds of materials- 
handling problems that can be eliminated through the 
implementation of a well-designed supply-handling system. 

Example 1 

At one mining operation visited by the Bureau, a haz- 
ardous lifting task could have been eliminated through 
improving the organization of the surface storage area. At 
this mine, workers needed to salvage a 250-lb timber that 
would be used to help support the roof in a particular 
section of the mine. Unfortunately, the timber had been 
indiscriminately tossed into a junk pile for storage, an area 
that no mechanical-assist device could access. Although a 
forklift was brought over to the junk pile, it could not get 
close enough to reach the timber. Therefore, it was nec- 
essary for two workers to lift the timber manually onto 
the forks. Obviously, this hazardous manual lifting task 
could have been prevented simply by stacking the timber 
neatly in an area where the forklift could easily approach 
it so that it could be lifted entirely through mechanical 
means. As this example suggests, the surface supply yard 
is one area where it is relatively easy to use standard 
mechanical-assist devices. In fact, manual lifting should 
rarely have to take place in a well-designed surface supply 
yard. 

Example 2 

A materials-handling system can encompass an entire 
mine and may even extend to the facilities of the mine's 
suppliers. For example, at the mine, the system may begin 
at the surface supply area and continue through delivery to 
underground locations. But, if necessary, it can also in- 
clude packaging and shipping operations at the supplier's 
plant. In fact, the manner in which supplies are received 
at the mine may determine the extent to which the sup- 
plies can be mechanically handled. For instance, the 
Bureau has observed some mines where supplies such as 
rock dust were delivered as hundreds of individual bags 
that had to be loaded manually onto supply cars. How- 
ever, it would have been just as easy for the supplier to 
deliver these items either on pallets or banded in unit 
loads, which could then be loaded mechanically onto the 
supply car, thus eliminating hundreds of heavy manual lifts. 
The mine in this example had a forklift available that could 
perform the lifts mechanically; however, because the ma- 
terials were not delivered to the mine in a suitable man- 
ner, the mechanical-assist device could not be used. Un- 
fortunately, many examples of under-utilization of available 
mechanical-assist devices exist in the mining industry. The 
great majority of loading operations on the surface can be 
performed through mechanical means, using just a forklift 
or a front-end loader. Close communication with the 
mine's supplier is crucial in designing a supply-handling 
system that uses mechanical-assist devices to the fullest 
extent possible. 



Example 3 

One of the most common tasks in underground coal 
mining is lifting and securing power cables to the mine 
roof so that equipment may pass freely through the mine. 
A simple way to eliminate this strenuous lifting task is to 
use lightweight cable ramps; the cable can now remain on 
the mine floor and is protected from harm (fig. 6). This 
is a direct application of the simplification principle of 
materials handling. 

A careful examination of the supply-handling system 
currently in operation at a mine will probably identify 
several materials-handling tasks that can be either elim- 
inated, reduced, or combined to improve the flow of sup- 
plies. Eliminating these unnecessary tasks can both 
improve the economy of the supply-handling system and 
greatly reduce the risk of injury to workers. 

USING TASK-SPECIFIC MECHANICAL- 
ASSIST DEVICES 

If a materials-handling task cannot be eliminated, the 
next solution to consider is whether a task-specific 
mechanical-assist device can be used or developed to 
accomplish the task, rather than having the job performed 
manually. This section describes the redesign of materials- 
handling tasks through the use of mechanical-assist de- 
vices. Included is a summary of Bureau research that has 
demonstrated that easily fabricated mechanical devices can 
be developed to assist with many specific underground 
materials-handling tasks. 




Figure 6.-Cable ramps eliminate manual lifting. 



10 



The previous section dealt with the steps to develop a 
system to handle the daily supply-handling needs in an 
underground coal mine. However, many of the more 
hazardous materials-handling activities occur during mine 
and equipment maintenance tasks (table 4), which are 
often performed infrequently. In its studies of the 
materials-handling problems in underground coal mines, 
the Bureau has concluded that these infrequent handling 
tasks are best addressed through the use of mine-specific 
materials-handling devices. "Mine-specific" means hard- 
ware tailored to the particular environmental and oper- 
ating characteristics of the individual mine. Unfortunately, 
the Bureau has discovered a lack of mechanical handling 
devices suitable for the underground environment. Specif- 
ically, there are virtually no mechanical assists to aid in the 
end use of an item. Therefore, the Bureau began to spe- 
cifically study materials-handling problems after supplies 
have been delivered underground and while they are being 
used during mine or machine maintenance. This research 
resulted in the categorizing of specific needs for under- 
ground materials-handling devices: 

1. Devices to lift, lower, and rotate machine compo- 
nents (weighing up to 2,000 lb) that need to be removed or 
replaced on mining equipment. 

2. Devices to lift or lower components up to 500 lb in 
and out of scoops and on and off railcars and other mobile 
vehicles. 

3. Devices to remove palletized materials from railcars 
and to transport them to working sections or supply areas. 

4. Devices to transport small quantities of materials 
weighing up to 500 lb from storage areas or rail headings 
to working sections. 

5. Devices to lift long, slender loads of up to 600 lb for 
roof support in haulageways or other areas of the mine. 

Table 4.-Hazardous mine and equipment maintenance 
tasks, 1980 data 



Days 


Activity 


Unit weight, 


Frequency 


lost 




lb 




5,961 . . 


Handling machine parts 
or tools. 


5- 200 


Weekly. 


4,639 . . 


Handling oil drums, grease 
cans, hydraulic oil. 


5- 50 


Daily. 


3,753 . . 


Handling cribbing, timber, 
props, and crossbars. 


50- 500 


Daily. 


3,022 . . 


Track maintenance .... 


100-1,000 


Monthly. 


2,862 . . 


Handling pumps, motors, 
gear boxes, wheel units, 
and other major compo- 
nents. 


200-2,000 


Monthly. 


1,675 . . 


Handling tires 


50- 200 


Weekly. 



Once these needs were identified, work was started on 
the designing and testing of practical, low-cost, easily fab- 
ricated materials-handling devices that were broadly appli- 
cable to underground operations. Where possible, the 
designs were simplified and off-the-shelf components were 
used to permit easy fabrication and modification of the 
devices by mine personnel to suit specific needs. 



Several task-specific mechanical-assist devices are pic- 
tured in figures 7 through 14, and are discussed below. 
Detailed plans for all of the devices are available through 
the Bureau (7). It is hoped that the simplicity and suc- 
cessful operation of this materials-handling hardware will 
inspire mine operators to investigate similar low-cost me- 
chanical solutions for reducing manual materials handling 
in their mines. 

Heavy-Component Lift-Transport 

One identified need was for a floor-type maintenance 
jack that could lift heavy machine components from the 
floor, transport them over short distances, and raise them 
into position for installation on face equipment. This type 
of device could be used to install drive motors under the 
nonremovable panels on shuttle cars or to replace heavy 
tires underground. 

The prototype of this device is pictured in figure 7. The 
device utilizes a hydraulic floor jack mechanism to provide 
the lift. The jackhead tilts and rotates to permit close-in 
maneuvering. The jack mechanism travels along the de- 
vice frame by means of a sump drive mechanism. This 
motion permits forward-backward movement of the com- 
ponents and balancing over the wheels of the device during 
travel. The long handle permits the user to have leverage 
to maneuver loads up, down, or sideways as required. 
Dual tires or oversized balloon tires increase the device 
stability and permit easy movement over uneven ground 
conditions. 

Beam-Raising Vehicle 

Manually lifting heavy wooden crossbeams or sections 
of rail for roof support is one of the most hazardous tasks 
in underground mining. A device was needed that could 
raise long, slender members, weighing up to 600 lb, and 
hold them in place against the roof while permanent sup- 
ports were installed. 

The prototype device is pictured during an underground 
test (fig. 8). This device uses a modified automotive floor 
jack to provide the lift, while special bearings allow the 
whole jack mechanism to roll down the center of the car 
for positioning the load. The jackhead also rotates to 
make load positioning easier. 

Scoop-Mounted Lift Boom 

Figure 9 demonstrates a simple boom device that can 
be quickly mounted on the front of a small scoop after the 
bucket has been removed. This boom can lift and trans- 
port components weighing up to 3,000 lb, such as a con- 
tinuous miner head. The scoop-mounted lift boom is a 
simple design that can be fabricated at the minesite and 
can be readily stored in working sections or on mobile 
machinery. This device can be installed or removed in 
5 m. a or less. 



11 




Figure 7.-Heavy-component lift-transport 




Figure 8.-Beam-raising vehicle. 



12 



-» A i 




Figure 9. -Scoop-mounted lift boom. 



Machine-Mounted Swivel Crane 



Container-Workstation Vehicle 



A lightweight, removable, and stowable lift crane is 
pictured in figures 10 and 11. This device can be installed 
on maintenance carts or on mining machines using inex- 
pensive mounts welded permanently at various locations on 
the machine frame. The height of the crane can be quick- 
ly varied from 24 to 68 in by changing the crane leg; the 
arm radius is variable from 24 to 48 in. The machine- 
mounted swivel crane can lift components (up to 500 lb) 
on and off transport vehicles and maneuver heavy machine 
components in confined spaces. This device can be carried 
by one person, mounts and stows without tools, and can be 
fabricated in a mine shop. 

Mine Mud Cart 

Figure 12 demonstrates a small, manually pulled cart 
that can transport up to 900 lb of materials over a short 
distance. The mine mud cart features balloon tires for 
easy transit through mud or water and over mine floors. 
The narrow width of the vehicle permits passage by a 
parked mining machine, and the handle is designed for 
pulling by one or two people. This device can also be 
locally fabricated. 



Tools and supplies required for many maintenance tasks 
can be mounted in a transportable container, as pictured 
in figures 13 and 14. The transportable container may 
function as a tool station, lubrication module, rock dust 
unit, fire and safety equipment storage unit, cable splicing 
module, etc. The container-workstation vehicle allows for 
rapidly interchangable containers that can be picked up or 
dropped off as needed and can carry up to 1,000 lb. Other 
features include balloon tires for transportation on unim- 
proved mine floor, adjustable ground clearance, and a 
towbar that can be adapted for towing behind utility vehi- 
cles. This device can also be fabricated in most mine 
shops. 

SYSTEMS APPROACH TO MATERIALS 
HANDLING 

As mentioned above, two alternative strategies include 
eliminating the task or utilizing mechanical-handling equip- 
ment to assist the workers. To the extent possible, these 
job redesign strategies should emphasize constructing an 
efficient and integrated materials-handling system-in other 
words, a systems approach to materials-handling. 



13 




■■ ■;■■■■■:■■■■■■;■■ ■ ... ■ 



Figure 10-lnstallation of machine-mounted swivel crane. 




Figure 1 1 .-Machine-mounted swivel crane in use underground. 



A systems approach to materials handling means that 
the various components for handling and storing supplies 
or components are integrated and considered as one entity, 
not just as a series of isolated steps haphazardly strung 
together. The systems methodology was originally applied 
to military and aerospace planning but recently has been 
used successfully in industrial materials handling. The 
same concepts are applicable to daily supply handling in 
the underground mining environment. 

The following list summarizes the major benefits that 
can be achieved by applying a systems approach to mate- 
rials handling in an underground mine: 

1. Better coordination with suppliers and customers. 

2. Fewer delays between mining operations. 

3. Higher levels of equipment utilization. 

4. Improved scheduling. 

5. Less material loss due to breakage. 

6. Lower labor costs. 

7. Reduced materials storage requirements. 

8. Safer, more systematic work procedures. 

Increased safety is of particular concern in underground 
mining. As mentioned, almost 35 pet of all reported lost- 
time mining accidents annually can be attributed to man- 
ually handling parts, supplies, or equipment. These acci- 
dents usually involve lifting, lowering, pushing, pulling, and 
related types of effort. A supply-handling system that 
makes use of mechanization can play a leading role in 
reducing these injuries. The introduction of even simple, 
manually operated types of carts and hoists can go a long 
way toward providing a safer workplace. While a properly 
designed supply-handling system can improve the safety of 
operations, it is imperative that engineers and managers 
make sure that any new equipment introduced as a part of 
the system does not introduce new hazards to the work- 
place. Possible hazards should be investigated before any 
new materials-handling equipment is purchased or fabri- 
cated. Also, periodic inspections are an important part of 
any materials-handling safety program. Detailed inspec- 
tion procedures and recommended frequencies are avail- 
able from most equipment dealers and manufacturers. 

There are many possible methods for handling mate- 
rials at any given mine. It is good practice, therefore, to 
begin the development of a systems approach to materials 
handling by considering the 20 principles of materials 
handling (8): 

1. Orientation Principle: Study the system relation- 
ships thoroughly prior to preliminary planning in order to 
identify existing methods and problems, physical and eco- 
nomic constraints, and future requirements. 

2. Planning Principle: Establish a plan to include 
basic requirements, desirable options, and the consider- 
ation of contingencies for all materials-handling and stor- 
age activities. 



14 




Figure 12.-Mine mud cart 




Figure 13. -Container-workstation vehicle. 



15 




Figure 1 4.-lnterchange of containers on container-workstation vehicle. 



3. Systems Principle: Integrate those handling and 
storage activities that are economically viable into a coor- 
dinated system of operation including receiving, inspection, 
storage, production, assembly, packaging, warehousing, 
shipping, and transportation. 

4. Unit Load Principle: Handle product in as large a 
unit load as practical. 

5. Space Utilization Principle: Make effective utili- 
zation of all cubic space. 

6. Standardization Principle: Standardize handling 
methods and equipment wherever possible. 

7. Ergonomic Principle: Recognize human capabilities 
and limitations by designing materials-handling equipment 
and procedures for effective interaction with the people 
using the system. 

8. Energy Principle: Include energy consumption of 
the materials-handling systems and materials-handling 
procedures when making comparisons or preparing eco- 
nomic justifications. 

9. Ecology Principle: Minimize adverse effects on the 
environment when selecting materials-handling equipment 
and procedures. 

10. Mechanization Principle: Mechanize the handling 
process where feasible to increase efficiency and economy 
in the handling of materials. 

11. Flexibility Principle: Use methods and equipment 
that can perform a variety of tasks under a variety of op- 
erating conditions. 



12. Simplification Principle: Simplify handling by elim- 
inating, reducing, or combining unnecessary movements 
and equipment. 

13. Gravity Principle: Utilize gravity to move material 
wherever possible while respecting limitations concerning 
safety product damage and loss. 

14. Safety Principle: Provide safe material handling 
equipment and methods which follow existing safety codes 
and regulations in addition to accrued experience. 

15. Computerization Principle: Consider computer- 
ization in materials-handling and storage systems when cir- 
cumstances warrant, for improved material and informa- 
tion control. 

16. System Flow Principle: Integrate data flow with the 
physical material flow in handling and storage. 

17. Layout Principle: Prepare an operational sequence 
and equipment layout for all viable system solutions; then 
select the alternative system that best integrates efficiency 
and effectiveness. 

18. Cost Principle: Compare the economic justification 
of alternative solutions in equipment and methods on the 
basis of economic effectiveness as measured by expense 
per unit handled. 

19. Maintenance Principle: Prepare a plan for preven- 
tive maintenance and scheduled repairs on all materials- 
handling equipment. 



16 



20. Obsolescence Principle: Prepare a long-range and 
economically sound policy for replacement of obsolete 
equipment and methods with special consideration to after- 
tax life cycle costs. 

These principles are based on the accumulated experi- 
ence of many experts in the field of materials handling and 
were compiled by the College-Industry Council on Mate- 
rials-Handling Education (8). As with any such listing, 
they should be viewed as general principles for locating a 
starting point in developing a solution. 

The elements of a materials-handling solution include 
personnel, equipment, facilities, capital, and time. The 
following questions should be answered during the formu- 
lation of a solution: 

1. What personnel will be involved? 

2. What training will be required? 

3. What type of supervision will be needed? 

4. How will production be affected (both positively and 
negatively)? 

5. How will maintenance be affected? 

6. What equipment will be needed? 

7. What new facilities will be needed? 

8. What will be the cost? 

Usually the primary technical factors to be considered 
when answering these questions are (1) a knowledge of 
the types of handling equipment available, (2) their ad- 
vantages and disadvantages, (3) their purchase, installation, 
and operating costs, and (4) their general utility in the 
mine. 

Questions concerning reliability, maintenance, compat- 
ibility, and other technical issues should be asked about 
any proposed solutions. If possible, simulation models or 
other quantitative techniques should be used to evaluate 
the alternatives. The various proposed solutions should 
also be tested against economic criteria, and all direct and 
indirect costs should be taken into account. 

After the technical and economic factors have been 
investigated, the intangibles must be considered. These 
items can make or break a solution and typically include 
the following: 

1. Potential increases in safety. 



2. Potential increases in morale. 

3. Job enrichment. 

4. Compatibility with established mining policy. 

5. Operating feasibility. 

6. Adaptability to future changes in the mining method. 

7. Adaptability for expansion (or reduction). 

Once a preferred solution has been identified, an im- 
plementation plan must be developed. Depending on the 
complexity of the proposed system, assistance may be 
required from equipment manufacturers, distributors, and 
systems contractors. After the system has been operating 
for a number of months, its performance should be au- 
dited to ensure it is justifying the investment. Additional 
engineering work and installation modifications may be 
necessary to fine-tune the operation. 

SUMMARY 

This chapter has presented the two most preferred 
strategies for reducing materials-handling injuries in un- 
derground coal mines: eliminating hazardous materials- 
handling tasks where possible and developing materials- 
handling hardware to meet specific materials-handling 
needs. After the redesigned tasks have been in operation 
for a few months, the changes should be reevaluated to 
ensure that all is proceeding as expected. Feedback should 
be solicited from the workers involved with implementing 
any changes in the supply-handling system, and additional 
engineering work and modifications may be necessary to 
fine-tune the operation. 

Based on contacts made during the course of this re- 
search, there appears to be a sincere interest on the part 
on mine management and safety and production person- 
nel in reducing materials-handling-related injuries. There 
is also the need for increased exposure to the types of 
materials-handling concepts presented in this chapter to 
stimulate further advances in addressing mine-specific 
materials-handling problems. Redesign of materials- 
handling activities through elimination of materials- 
handling tasks and the use of mechanical-assist devices 
represents the best method for reducing the cost and 
incidence of manual lifting injuries. 



CHAPTER 3.-MATCHING JOB DEMANDS TO WORKER CAPABILITIES 



Although redesign of the supply-handling system 
through task elimination and use of mechanical-assist 
devices represents the best opportunity to reduce muscu- 
loskeletal injuries, there will be some jobs where such 
changes are not possible. Ultimately, miners have to lift 
heavy materials to perform necessary underground mining 
tasks. However, there are methods that can reduce the 
risk of back injury, even when manual lifting must take 
place. As indicated in figure 1, the key to redesigning 
manual lifting tasks is to match the demands of the job 



to the physical capability of the worker to perform that 
job. For instance, the posture adopted by an underground 
miner to perform a lifting task can have a very consid- 
erable effect on how much weight is safe to lift. There- 
fore, if workers have to lift in certain postures, the risk of 
injury may be reduced by packaging materials in weights 
that do not exceed the amount considered safe to lift in 
those postures. Furthermore, certain lifting positions 
may cause workers to fatigue more quickly than others. 
In this case, the risk of injury can be reduced by providing 



17 



adequate rest so that muscular fatigue does not become 
the cause of a lost-time injury. 

This chapter discusses redesign of manual lifting tasks 
according to the physical capabilities of underground min- 
ers as another useful method of reducing the incidence 
and cost of back injuries in low-seam coal mines. To 
better understand the stresses experienced by the low back 
during lifting tasks, a brief section describing the anatomy 
of the back and the causes of low-back pain is provided 
followed by a discussion of methods used by researchers 
to recommend acceptable lifting limits. The results of 
Bureau studies are then provided, which describe ways in 
which the lifting capacity of miners is affected by working 
in stooped and kneeling postures. The implications of 
these studies in terms of redesign of manual lifting tasks to 
reduce the worker's risk of injury are discussed. 

ANATOMY OF THE BACK AND CAUSES 
OF LOW-BACK PAIN 

When a worker lifts manually, the body (especially the 
low back) is subjected to significant physical strain. This 
is the reason that the number of manual lifting tasks 
should be reduced to the absolute minimum necessary. 
To better understand the load placed on the body when 
lifting and to identify the reasons workers experience back 
injuries, a basic understanding of the anatomy of the back 
is necessary. 

The spine comprises 33 or 34 bones called vertebrae. 
These vertebrae are divided into five specific regions ac- 
cording to structure and function (fig. 15). The neck or 
cervical region comprises seven bones primarily designed 
to support the head. The midback or thoracic section of 
the spine contains 12 bones that get progressively larger 
down the spine. The thoracic vertebrae are the bones to 
which the ribs are attached. The low back or lumbar 
region of the spine contains five of the largest bones of the 
vertebral column, upon which the majority of the weight 
bearing of the trunk and head occurs. This is the region 
of the spine where the greatest strain is experienced when 
lifting, and it is not surprising that this is the region where 
the majority of back injuries occur. The lower two sec- 
tions of the spine (the sacrum and coccyx) are made up 
of smaller, fused vertebrae. 

The bones of the cervical, thoracic, and lumbar sec- 
tions of the vertebral column are separated by oval, shock- 
absorbing intervertebral (IV) disks. The IV disk has two 
distinct sections (fig. 16). The outer portion of the disk is 
composed of tough ligamentous fibers that are arranged in 
a crisscross fashion, much like the plies on a radial-belted 
tire (9). The inner portion of the IV disk is made of a soft 
substance with the consistency of jelly. This part of the 
disk is what gives the disk its cushiony character. Experts 
believe that many back injuries are caused when the strong 
muscles of the back contract so vigorously that these disks 
are compressed so that the nerves exiting the spine at the 
lumbar region become "pinched," causing the muscles of 
the region to spasm, thus producing low-back pain. 







HL-rsA^Cl 






Atlas 


t-£+S c 2 




Cervical * 


Axis- 










Jk3Xjc6 | 








£3*¥c7 A 

v^=y T2 
?e^T3 

AS T5 








JtEs T6 








jg T7 




Thoracic < 




joI T9 

$5tz4TIO 






| 


C§S§,TI2 






r -- = i 






Lumbar < 




v§3 L3 






^rzjr-^r^r^ 


r&J&T — 


Sacrovertebral 


Sacral < 




W W\rticu 


joint 




#■' 


ar portion 


Coccygeal {_ J? 


\ of 


sacrum 



Figure 1 5.-Vertebral column. (Courtesy W. B. Saunders Co.) 



Anterior 

longitudina 

ligament 



Disk 




Posterior 
articular 
capsule 



Figure 16.-lntervertebral disk. A, Separating two vertebral 
bones; B, Isolated view. Note the alternating layers of fibers 
permitting limited movement in all directions. (From "Oh, My 
Aching Back," by L Root and T. Kiernan, 1975; reprinted by 
permission of David McKay Co., a division of Random House, 
Inc.) 



18 



The vertebral column has many muscles associated with 
it; these allow controlled movements of the trunk and 
provide additional support to the spine. During lifting 
tasks, the muscles of the back may generate more than 
1,500 lb of force to perform the lift. Obviously, the con- 
tractile forces exerted by these muscles put a large amount 
of compressive strain on the vertebral column. The key to 
redesigning lifting tasks is to reduce the amount of force 
required of these muscles to moderate levels to reduce the 
compressive loading on the lumbar spine. Not only does 
this decrease the compressive load, it also decreases the 
probability of back muscle strain-another common cause 
of low-back pain. 

Finally, the spine also has numerous ligaments asso- 
ciated with it. These ligaments are tough, fibrous bands 
of tissue that help to support the vertebral column. Liga- 
ments are flexible, but only to a limited degree. There- 
fore, ligaments can be stretched only a small amount be- 
fore they tear or rupture. If this occurs, instability and 
abnormal motion may occur, which may also lead to low- 
back pain. 

METHODS OF DETERMINING 
LIFTING CAPACITY 

There are three primary techniques used when re- 
searchers attempt to determine an acceptable weight of 
lift for a given task. These techniques are the biomechan- 
ical approach, the physiological approach, and the psycho- 
physical approach. The biomechanical approach attempts 
to calculate the stresses experienced by the low back dur- 
ing materials-handling tasks and is generally useful for 
evaluating low-frequency lifting activities (10). The phys- 
iological approach uses measurements such as heart rate, 
oxygen consumption, and ventilation volume to establish an 
acceptable work load when lifting (10-11). The psycho- 
physical approach allows test subjects to adjust the amount 
of weight contained in a lifting box to the amount they feel 
can be handled without undue stress or fatigue under 
specified conditions (12). Each of these methods has 
advantages and limitations, which are discussed in the 
following sections. 

Biomechanical Approach 

During manual lifting tasks, the lumbar region (low- 
back region) of the spinal column is subjected to much 
greater loads than any other area of the spine, and it is the 
region where most back injuries occur. The biomechanical 
approach to establishing lifting limits attempts to calculate 
the compressive load and shear forces imposed on the 
lumbar disks during materials-handling activities (11). The 



reason for the high forces produced on the lower back 
during lifting activities is the vigorous contraction of back 
muscles to counteract the mass of the weight being lifted 
(13). 

An example of the biomechanical stresses experienced 
by the low back during a lifting task is shown in figure 17. 
As indicated in this figure, just holding a 50-lb box 1.75 ft 
in front of the spine requires the muscles of the low back 
to exert 700 lb of force. These muscles need to produce 
such a large amount of force because they are positioned 
so close to the spine (1-1/2 in away), yet they are having 
to counterbalance a weight that is 21 in from the spinal 
column (fig. 17/1 ). However, if one brings the weight 
closer to the body, so that it is only 1 ft in front of the 
spine (fig. 175), only 400 lb of force is required of the 
back muscles. Reducing the force exerted by the back 
muscles has the effect of diminishing the load experienced 
by the spine and thus decreases the risk of back injury. 
This biomechanical principle is the reason that workers are 
always instructed to "keep the load close" when lifting. 
From this example, it can be seen that calculating the 
biomechanical strains of lifting can help to redesign tasks 
so the stress on the low back is decreased. The biome- 
chanical analysis technique can be extremely useful in 
determining the strain experienced by the low back in 
manual lifting tasks. 



B 





0.125 ft x muscle force = 

1.75 ft x 50 lb 
Muscle force = 700 lb 



0.125 ft x muscle force = 

I ft x 50 lb 
Muscle force =400 lb 



Figure 17.-Example of biomechanical stresses. A, Holding an 
object at a far distance from the spine requires a tremendous 
amount of force to be developed by the back muscles; B, the 
amount of force can be reduced by holding the object closer to 
the body. 



19 



Physiological Approach 

This approach to establishing acceptable weights of lift 
relies on physiological measurements such as heart rate, 
oxygen consumption, or ventilatory volume to determine 
the amount of work a person can perform without undue 
fatigue (10). The physiological cost of muscular work can 
be easily determined by measuring the oxygen that is used 
during physical work (14-15) (fig. 18). When muscles 
become active, their increased metabolic demand spurs an 
increase in oxygen delivery by the heart and lungs. This is 
the reason for the higher heart rate and rate of breathing 
experienced during exercise or heavy work. This means 
that the difficulty of work being performed by an individual 
can be established. It is also well known that the harder 
an individual is working, the more quickly the muscles 
become fatigued. When muscular fatigue occurs, the 
worker may be more prone to injury (14). 

Several factors are known to affect the physiological 
responses to lifting weight. These can be divided between 



worker variables and task variables (4). Among the major 
worker variables are gender, body weight, and the lifting 
method or technique used. The task variables may include 
the weight of the load, the frequency of lifting, the vertical 
distance the load is moved, and the temperature and hu- 
midity of the workplace. The NIOSH work practices guide 
(4) recommends that for occasional lifting (for 1 h or 
less), the metabolic energy expenditure rate should not 
exceed 9 kcal/min for physically fit males or 6.5 kcal/min 
for physically fit females. These metabolic expenditure 
rates correspond to oxygen consumption rates of 1.8 and 
1.3 L/min, respectively. Heart rates for these tasks should 
not exceed 140 beats per minute for males or 120 beats 
per minute for females. Likewise, continuous (8-h) lim- 
its should not exceed 5.0 kcal/min for healthy males or 
3.5 kcal/min for healthy females. The corresponding 
oxygen consumption rates are 1.0 and 0.7 L/min, respec- 
tively. Heart rates for these longer duration tasks are 
110 beats per minute for males and 100 beats per minute 
for females (4). 




Figure 18.-Analyzing subject's expired air. 



20 



Psychophysical Approach 

The third major method utilized in assessing lifting 
capacity is the psychophysical approach. The psychophys- 
ical approach assumes that the biomechanical and physio- 
logical stresses experienced by an individual during a lifting 
task are combined into a single measure of perceived 
stress (10, 12). The use of psychophysics in tests of lifting 
capacity generally allows the subject to be in control of the 
weight of the container being lifted. The subject is asked 
to adjust the weight of the box so that the lifting task does 
not lead to undue fatigue or overexertion (16-17). When 
this approach is used, two periods of lifting are common, 
one starting with a light box and one starting with a heavy 
box (18). The average weight chosen at the end of these 
two lifting periods is taken as the maximum acceptable 
weight of lift (MAWL) for the given task conditions (the 
frequency of lift, container size, posture, etc.). 

The psychophysical method of determining permissible 
loads has many advantages. Psychophysics allows the 
realistic simulation of industrial work; for example, the 
lifting task can be a dynamic lift through a given distance. 
The frequency of lift may be varied to include either fast 
or slow rates, and intermittent tasks commonly found in 
industry can be examined. In addition, psychophysical 
results are very reproducible and appear to be related to 
low-back pain (19). The main disadvantage of the method 
is the fact that it is subjective, and it will probably be re- 
placed when objective methods (such as biomechanical 
modeling) become more reliable. 

Comparison of the Approaches 

It has been suggested that the psychophysical approach 
may be the best single measure when determining accept- 
able weight-lifting burdens (10). The problem with using 
either the physiological or biomechanical approach alone 
to evaluate lifting capacity is that almost all lifting tasks 
have both biomechanical and physiological stresses asso- 
ciated with them. Furthermore, it is often the case that a 
particular lifting task may be within recommended limits 
for one of these methods, while exceeding the limits for 
the other. For example, lifting a very heavy weight one 
time does not require a very high expenditure of energy 
(and thus would be acceptable using physiological stan- 
dards), but the biomechanical stresses associated with such 
a task might well exceed recommended limits. Conversely, 
lifting a lighter weight repetitively may be acceptable in 
terms of biomechanical stress, but the metabolic cost of 
the repetitive task would be greater and may exceed safe 
physiological limits. 

In general, manual materials-handling recommendations 
based upon the biomechanical method tend to suggest 
lifting lighter loads more frequently. On the other hand, 
physiological models tend to advise lifting heavier loads 
less frequently (10). The preceding examples demonstrate 
that lifting is a complex task whose stresses cannot be fully 
explained by either the biomechanical or physiological 
approach alone. The virtue of the psychophysical 



approach is that it attempts to integrate the biomechanical 
and physiological stresses of a lifting task into a single 
measure of perceived stress. 

BUREAU OF MINES LIFTING 
CAPACITY STUDIES 

While a great deal of research has examined the lifting 
capacity of workers in unrestricted lifting postures, very 
little is known about the lifting capacity of underground 
miners in the restricted postures they must assume in low- 
seam coal mines. Therefore, the Bureau examined the 
lifting capacity of underground miners in stooped and 
kneeling postures. The results of these studies demon- 
strate how changes in posture can dramatically affect a 
miner's lifting capacity. Only the general findings of these 
studies are presented in this chapter; however, more detail 
can be found elsewhere (20-22). 

The Bureau examined the lifting capacity of 25 under- 
ground miners (all members of the United Mine Workers 
of America) in both stooped and kneeling positions in two 
separate studies. The lifting task was asymmetric and was 
designed to simulate the unloading of a supply car in a 
low-seam mine (fig. 19). Both studies examined lifting 
capacity using the psychophysical method. As described 
previously, this method allows the miners to adjust the 
amount of weight in a lifting box according to their sub- 
jective estimate of lifting capacity in each posture— stooped 
or kneeling. There were two lifting periods in each pos- 
ture: one starting with a light box (approximately 25 lb), 
the other starting with a heavy box (approximately 95 lb). 
The subjects were instructed to adjust the amount of 
weight in the lifting box by putting in or taking out steel 
weights until they reached the amount of weight they could 
handle without undue stress or fatigue. Periods of lifting 
were 20 min in duration, and the frequency of lifting was 
10 per minute, a lifting frequency that the Bureau found 
to be about the average for compact, repetitively handled 
loads (23). The maximum acceptable weight of lift was 
taken as the average of the weight of the boxes from two 
lifting periods in each posture. The miners were not 
aware of the amount of weight they were lifting. 

Lifting Capacity of Underground Miners 

These studies demonstrated that miners have a signif- 
icantly lower lifting capacity in the kneeling posture than 
in the stooped posture. In fact, the average miner lifted 
about 10 lb less in the kneeling posture than when 
stooped. The data in these two studies were used to es- 
tablish recommended lifting limits for repetitively handled 
materials in underground coal mines. Such materials may 
include items such as rock dust bags, ventilation stopping 
blocks, crib blocks, roof bolts, cans of hydraulic oil, and 
other compact, frequently lifted supply items. The recom- 
mended maximum weights of lift for repetitively handled 
items in the stooped posture is 55 lb, while the recom- 
mended maximum weight of lift for these items in the 
kneeling posture is only 45 lb. The miners used in these 



21 




r yf i — 








Figure 1 9.-Underground miners performing lifting capacity tests at Bureau of Mines Ergonomics Laboratory. 



lifting studies were probably in better physical condition 
than other miners, owing to the thorough medical 
screening performed. This medical screening included a 
thorough physical examination and graded exercise tol- 
erance test (21). Furthermore, any candidates with prior 
history of lost-time back injury were excluded from par- 
ticipation. Therefore, the recommended weights described 
here may exceed the amount that less healthy miners can 
safely lift. 

The results of the Bureau's lifting capacity tests have 
useful implications for proper design of materials that 
must be lifted in low-seam coal mines. Perhaps the most 
commonly handled material in underground coal mines is 
a 50-lb rock dust bag. While the 50-lb weight is less than 
the recommended limit for the stooped posture, it exceeds 
the recommended weight for the kneeling posture. Results 
of the Bureau's studies indicate that compact, repetitively 
handled supplies in low-seam mines should be packaged 
in containers weighing less than 45 lb (the recommended 
limit for lifting in the kneeling posture), because of the 
decreased lifting capacity of miners in the kneeling 
posture. 

It should be noted that these recommended limits apply 
only to repetitively handled materials such as those listed 
above. When materials are lifted at a lower frequency, it 
would be expected that somewhat greater weight could be 
lifted. However, a recent Bureau study has shown that 
lifting capacity is significantly lower in the kneeling posture 
than stooped, even with lower frequency materials-handling 
tasks. 

Physiological Stress of Lifting 
in Restricted Postures 

Results of the physiological measurements taken during 
the lifting capacity tests indicated that, despite the fact that 
miners lifted less weight in the kneeling posture, the phys- 
iological cost of lifting in this posture was actually greater 



than that experienced when stooped. Heart rate, oxygen 
consumption, and ventilation volume were all found to be 
significantly higher in the kneeling position. This indicates 
that workers may fatigue more quickly when lifting in the 
kneeling posture. While lifting tasks in underground mines 
are generally sporadic enough to allow sufficient rest, more 
frequent rest breaks should be allowed when miners must 
handle materials for prolonged periods in the kneeling 
posture to reduce the risk of injury due to fatigue. 

Biomechanics of Lifting in Restricted Postures 

Analysis of data collected relating to muscular activity 
of trunk muscles (electromyography) during the lifting 
tasks indicated that the large muscles of the lower back 
contracted much more vigorously in the kneeling posture 
than in the stooped posture. This implies a greater com- 
pressive loading on the spine while kneeling, hence a 
greater chance of back injury. Apparently, the back mus- 
cles take on added responsibility for lifting when kneeling, 
because of the reduced muscle mass available to perform 
the work. In the stooped posture, the worker has more 
use of the leg muscles to help with the lift and can there- 
fore execute a whole-body exertion. This may be one 
reason why the lifting capacity is higher in the stooped 
posture. 

Results of an experiment investigating the effect of 
posture on back strength indicate that back strength is 
decreased by about 10 to 15 pet when kneeling (20). This 
fact may help to explain the lower lifting capacity demon- 
strated in the kneeling position. The diminished force- 
producing capability of the back muscles in this posture 
may also help to explain the fact that these muscles dem- 
onstrate greatly increased activity when a person is lifting 
in the kneeling posture. It would seem reasonable to 
assume that these muscles would have to work harder to 
perform a lift when a person is kneeling if their overall 
strength capability in this position is decreased. 



22 



Both postures commonly used for manual lifting in 
underground mines present serious problems for the work- 
er, and neither posture should be used for lifting unless it 
is unavoidable. The lifting studies showed that kneeling is 
a very stressful posture in which to lift. The lifting ca- 
pacity of underground miners is significantly lower in the 
kneeling posture than when stooped. This is due to the 
reduced amount of muscle that can be used to perform the 
lift when kneeling. In addition, the physiological cost of 
lifting is higher when kneeling-workers are likely to 
fatigue more quickly when lifting in this posture. The low- 
back muscles contract much more vigorously in the kneel- 
ing posture, indicating that the compression on the disks 
of the spine may be increased in this posture. This in- 
crease in muscular activity also indicates that the chances 
of muscular strain may be increased when lifting in the 
kneeling posture. 

While the stooped posture appears to have some advan- 
tages over the kneeling position (that is, increased lifting 
capacity, lower metabolic cost, and less back muscle activ- 
ity), the stooped posture is also very hazardous (75, 24-27). 
This posture can put a large amount of loading on the lig- 
aments of the low back, which contain many pain-sensitive 
nerve endings; many researchers feel that stressing these 
ligaments leads to low-back pain (27). This indicates that 
the chances of a ligament sprain may be increased in the 
stooped posture. In addition to the ligament stress ex- 
perienced in the stooped posture, the spine is in a very 
flexed position, which causes a great deal of pressure on 
the rear portion of the disks of the lumbar spine. Many 
researchers agree that this may cause low-back pain by 
caus-ing the back of the disk to deform in the area where 
many pain-sensitive nerves are present (13, 24-27). 

Given the previous information, how can the chances 
be reduced that a worker will experience a low-back in- 
jury in these two stressful postures? It is important to 
reduce the amount of weight of supplies that are handled 
in the kneeling posture (because of the reduced lifting 
capacity observed while kneeling). This reduces the 
chances that the miner will overstrain back muscles when 
kneeling. In addition, reducing the weight of supplies 
decreases the likelihood that muscular fatigue will be the 
cause of a lost-time injury. 

While Bureau research has demonstrated that miners 
have an increased lifting capacity in the stooped posture, 
lifting periods in this posture should not be prolonged, 
because of the strain placed on the intervertebral disks and 
the ligaments of the lumbar spine. When miners lift in a 
stooped posture, they should perform back extension ex- 
ercises to reduce the strain on the disk and ligaments, and 
to restore the lordosis (forward curvature) of the lumbar 
spine. Chapter 5 describes an exercise called the prone 
pushup, which is an excellent exercise after working in a 
stooped posture. This exercise can be performed in almost 
any low-seam coal mine and, if performed correctly, may 
significantly improve the back status of underground coal 
miners. 



REDESIGNING MANUAL LIFTING TASKS 
TO MINER'S PHYSICAL CAPABILITIES 

The Bureau studies described above indicate that the 
posture used for an underground lifting task has a signif- 
icant effect on the ability of the miner to accomplish the 
task. The job demands placed on the worker need to 
match the capabilities of the worker when performing 
materials-handling tasks in restricted postures. The results 
of the lifting studies can be used to recommend proce- 
dures that should be followed when lifting in the restricted 
postures that must be assumed in low-seam mines. 

Maximum Recommended Weights of Lift 

The results of the psychophysical tests of lifting capacity 
of underground coal miners have demonstrated that the 
lifting capacity of miners in the kneeling posture is signif- 
icantly lower than that of miners in the stooped posture. 
An acceptable weight of lift is defined as one that 90 pet 
of the working population are able to lift using the psycho- 
physical methodology (28). Using this criterion, the maxi- 
mum recommended weights of lift for repetitively handled 
materials in low-seam coal mines are 55 lb in the stooped 
posture and 45 lb in the kneeling posture . Because miners 
are likely to use the kneeling posture for all commonly 
handled supplies at some time or another in low-seam 
mines, all compact, repetitively handled materials should 
be packaged in a weight not exceeding 45 lb. 

Redesign of Materials 

The results of the lifting capacity studies indicate that 
serious consideration should be given to redesigning repet- 
itively handled materials to conform to the recommended 
weight of lift in the kneeling posture. For example, rock 
dust bags might be reduced in weight from the current 
50-lb bag to a 40-lb bag. Similarly, other repetitively han- 
dled materials should be redesigned to match the demon- 
strated lifting capacity of underground miners in these 
postures. 

It is clear that the materials delivered to low-seam 
mines by the supplier have been packaged in weights that 
have been shown to be acceptable when a worker is able 
to lift in a standing posture. However, the results of these 
Bureau studies indicate these weights are not appropriate 
when workers have to Oft in the restricted postures char- 
acteristic of low-seam mines. The lifting posture has an 
important influence on the amount of weight that is safe 
to lift, so that workers are not subjected to a high risk of 
injury when they have to lift in awkward positions. An 
analysis of back injuries in coal mines has indicated that 
the rate of back injuries was higher in coal seams less than 
48 in than in seams thicker than 48 in. This may be due 
to the fact that workers are being required to lift weights 
that actually exceed their lifting capacity in the kneeling 
posture. Redesigning the weight of repetitively handled 



23 



supplies according to the recommended limits described 
above may significantly reduce both the incidence and cost 
of back injuries in low-seam coal mines. 

Handling Heavy Weights 

Given a choice of handling a heavy weight (>50 lb) in 
the stooped or kneeling position, it may be better to han- 
dle the weight stooped, because of the higher lifting ca- 
pacity demonstrated in this posture. Because more mus- 
cles can be called upon to lift in the stooped posture, this 
posture may be better, though admittedly not a great deal 
better, for handling compact, heavy loads (fig. 20). Since 
the spine is severely flexed in the stooped posture, a back 
extension exercise (such as the one presented in the back 
fitness program in chapter 5) should be performed after 
lifts in the stooped posture (27). 

Reducing Lifting Frequency 

If the weight of the object cannot be reduced, it is pos- 
sible to decrease the stress of the lifting task by having the 
worker reduce the number of times that the object is lifted 
per minute. This not only reduces the amount of stress 
experienced by the spine per minute, it also reduces the 
physiological cost of lifting, thus delaying the onset of 
muscular fatigue. 

Need for More Frequent Rest 
Breaks When Kneeling 

Metabolic demands may be increased when handling 
materials in the kneeling posture. In fact, the underground 
miners tested to date have demonstrated that both heart 
rate and ventilation volume have been significantly higher 
in the kneeling posture than stooped, despite the fact that 
significantly less weight was lifted when kneeling. Many 
studies have made it clear that activities with higher met- 
abolic demands require more frequent rest intervals. 
Therefore, to prevent the onset of muscular fatigue that 
may ultimately lead to musculoskeletal injury, more fre- 
quent rest breaks may be necessary in the kneeling posture 
(fig. 21) when prolonged manual lifting is performed. 

Stresses of Lifting When Stooped 

Certain individuals were not as tolerant to long periods 
of working in the stooped posture, even though these in- 
dividuals lifted more weight in this position. These sub- 
jects were generally those who had previous incidence of 
low-back pain. Overweight individuals also tended to be 
more sensitive to stooped materials handling. Therefore, 
it is suggested that individuals who have experienced seri- 
ous low-back pain or who are overweight exercise partic- 
ular caution when handling materials while stooped. 
Shorter periods of materials handling in this posture are 
indicated for such individuals to prevent reoccurrence of 
low-back pain (fig. 22). 




Figure 20.-Mlners have higher lifting capacity when stooped. 




Y- i% 




Figure 21 .-Miners may fatigue more quickly when kneeling. 




I 



Figure 22.-Stooped posture may be less tolerable for some 
miners. 



24 



In addition, activities involving prolonged stooping 
should be interrupted regularly by either standing upright 
(if possible) or performing the back extension stretch 
described in chapter 5 in the back fitness program. If 
possible, a lumbar lordosis should be maintained when 
lifting in the stooped posture. 

Modification of Work Environment 

If supplies have to be stored in an underground area, 
mine management should seriously consider cutting 
enough roof to create a storage area where the miners can 
stand upright when loading and unloading vehicles. Con- 
sidering the compensation costs (and other related costs) 
associated with lost-time back injuries, it seems quite ap- 
propriate to look for any possible method to reduce the 
loading to a worker's lower back. If the roof is cut, the 
supplies can be stacked on pallets or other support mate- 
rials that are at knee height, not ground level. Research 
(29) has shown that a worker is three times more likely 
to experience a back injury when lifting from the ground 
than from knee height. Thus, cutting roof so that workers 
can stand upright would reduce the severe biomechanical 
strain placed on the workers' backs when they bend over 
to pick up items from the floor. The costs involved with 
cutting the rock from the roof and properly supporting the 
area can be far less than the direct and indirect costs of a 
lost-time back injury. 

Lifting Technique 

While the amount of weight that is safe to lift in re- 
stricted postures is lower than that which is acceptable in 
unrestricted postures, many of the traditional principles 
of safe lifting are applicable to underground manual 
materials handling. The following section summarizes 
many of the important factors that apply to performing 
manual lifting tasks in low-seam mines, no matter which 
posture is adopted. 

Use a Smooth Lifting Motion 

Research has indicated that sudden or unexpected 
movements are responsible for a large number of back 
injuries. The sudden load experienced by a worker's back 
in this situation is often two to three times as great as 
when the load is expected (30). Related to this concept is 
the recommendation that if an object is stuck underneath 
other materials, do not attempt to lift it without first re- 
moving the debris on top of it. Two problems can be 
caused by this situation. First, the object may not move 
when the worker expects it to; this causes a very high load 
to be experienced by the lower back. Second, the object 
may pull free unexpectedly, which also places the low back 
under extremely high stress. 



Keep the Load Close to the Body 

The principles of biomechanics (discussed earlier in 
chapter 3) indicate that the further the load is from the 
spine, the greater the stress to the low back. Therefore, it 
is important to keep the load close. While restricted 
postures may limit how close the load can be to the body, 
it is still much better to handle the material so that the 
load is as close to the body as is practicable. 

Avoid Excessive Twisting 

Many researchers are of the opinion that the worst 
action when lifting is twisting. Twisting puts a severe 
strain on the fibers of the intervertebral disk and may 
actually cause some of these fibers to break, which severely 
weakens the disk. Furthermore, it is the opinion of some 
researchers (26) that injuries to the disk caused by twisting 
are much less likely to heal than injuries to the disk due to 
simple bending. Therefore, it is important to position the 
body so that a minimum of twisting is required to perform 
a lifting task (fig. 23). 

Get Help for Heavy Objects 

Many back injuries occur when a person tries to lift 
more weight than one individual can safely lift. Waiting a 
little extra time for help may prevent back injuries that 
may plague workers for the rest of their lives (fig. 24). 




Figure 23.-TwlsUng during a lift 



25 




X 




/ 



A 



* 



\J 



Figure 24.-Miners assisting one another with heavy load. 



SUMMARY 

While elimination of lifting tasks and use of mechanical- 
assist devices are the best methods of reducing materials- 
handling injuries, it is not always possible to redesign jobs 
using these methods. This chapter has presented another 
method that can be useful in reducing injuries experienced 
in low-coal mines-matching the lifting demands of a job 
to the worker's lifting capabilities. For instance, Bureau 
studies have indicated that the lifting capacity of miners 
is significantly lower in a kneeling posture than when 
stooped. In fact, the maximum recommended weight of 
lift for compact, repetitively handled materials (such as 
rock dust bags, stopping block, crib block, etc.) is 55 lb in 
the stooped posture, but only 45 lb in the kneeling posture. 
Furthermore, the physiological demands on the body are 
increased when kneeling, even though less weight may be 
lifted in this posture. This indicates that miners fatigue 
more quickly in the kneeling posture than when stooped. 
Reducing the weight of materials that must be manually 
handled in the restricted postures used in low-seam coal 
mines may significantly reduce back injuries due to over- 
exertion in underground lifting tasks. 



CHAPTER 4.-EXAMPLES OF ALTERNATIVE REDESIGN STRATEGIES 



This chapter provides examples of alternative strategies 
in the redesign of materials-handling tasks in low-seam 
coal mines. The examples follow the model for redesign 
of materials-handling tasks shown in figure 1. According 
to this model, once a materials-handling problem has been 
identified, the first step is to try to find a way that the job 
can be eliminated. If this solution is not feasible, the next 
step is to use or develop a mechanical-assist device to 
perform the job in order to eliminate the need to manually 
lift materials. If neither of these options is possible, an 
attempt should be made to modify the lifting task so that 
it does not exceed the lifting capacity of underground 
miners working in restricted postures. While it is usually 
possible to use one of these three methods, occasionally no 
physical redesign of the job or workplace is possible. In 
such cases, worker selection and training procedures are 
needed. Some of the following examples are based upon 
successful redesign strategies already implemented by 
some low-seam coal mines, which have not only reduced 
the risk of injury to the workers but have also increased 
the productivity of the crew. This chapter also discusses 
implementation and evaluation of redesign strategies. 

ELIMINATION OF MATERIALS- 
HANDLING TASKS 

A task analysis at a low-seam coal mine has determined 
that many supplies are handled excessively once the supply 
car reaches the underground storage section (31). As an 
example, when the supply car arrives at the storage point, 
400 heavy items (for example, rock dust bags, concrete 
block, etc.) are unloaded from the car onto supply piles, 



after which the supply car returns to the surface for an- 
other load. Eventually the stacked supplies are handled 
again to be transported to the production section for their 
end use. Therefore, a total of 800 manual lifts are re- 
quired in the storage section alone. 

One mine has found that the number of lifts can be 
dramatically reduced by keeping the supplies stored on the 
supply car in the storage area. This strategy immediately 
eliminates 400 of the manual lifts required in the storage 
section (unloading the supply car and stacking materials 
onto piles), each one of which may be a potential cause of 
a lost-time injury. The supplies now need to be manually 
handled only once-from the supply car to the scoop for 
transportation to the area of end use. In addition, the 
mine has found that this strategy can help keep supplies 
palletized and lifted through mechanical means almost 
exclusively. In fact, some supplies at this mine are handled 
manually only once-during the end use of the item. All 
other times, the supplies are handled as unit loads by 
forklift or by scoop. Obviously, this strategy may require 
the purchase of additional equipment (supply cars) that 
can be stored underground. However, when the costs of 
not using this strategy (for example, costs of lost-time 
injuries, decreased productivity of the crew, etc.) are to- 
taled, any purchase that can decrease the risk of back 
injuries can indeed be a cost-effective and wise investment. 
In fact, prevention of just one lost-time back injury may 
pay for the investment in the extra equipment. Elimi- 
nating materials-handling tasks is the best method for 
controlling the costs associated with back injuries in un- 
derground coal mines. 



26 



REDESIGNING MATERIALS-HANDLING 
TASKS USING MECHANICAL- 
ASSIST DEVICES 

An accident analysis by an eastern coal mine demon- 
strated that all members of a four-person crew had ex- 
perienced lost-time injuries due to lifting heavy rail (ap- 
proximately 550 lb) for roof support. Obviously, this is not 
a materials-handling task that can be eliminated- the roof 
needed to be supported by sections of rail. If a materials- 
handling chore cannot be eliminated, the next best strategy 
is to utilize or develop a mechanical-assist device to ac- 
complish the task. Such a device was discussed in chapter 
2 of this report, the beam-raising vehicle. This device uses 
a modified automotive floor jack to raise beams for roof 
support. The beam-raising vehicle effectively eliminates 
the need to manually lift these beams, thus avoiding the 
risk of injury due to an extremely heavy lifting task. Since 
this device has been put into service, the crew has not 
experienced any lost-time injuries due to performance of 
this job and has also become significantly more productive. 
It should be emphasized that the design of this device is 
simple enough that most mine shops could fabricate this 
piece of equipment on their own. The plans for this 
mechanical-assist device (and others described in chapter 
2) are available from the Bureau (7). 

REDESIGNING LIFTING TASKS TO FIT 
WORKER LIFTING CAPACITY 

A task analysis at a small low-seam coal mine has in- 
dicated that the most commonly handled supply items at 
the mine are rock dust bags, which weigh 50 lb. While this 
mine has eliminated and mechanized several of the steps 
in the transfer of rock dust, there are still significant pe- 
riods of repetitive manual lifting of these bags needed 
underground in severely restricted lifting "postures. In 
many low areas of the mine, the only posture that can be 
used to lift these bags is the kneeling posture. However, 
the 50-lb weight of these bags exceeds the recommended 
weight of lift for repetitively handled materials in the 
kneeling posture, according to the lifting capacity studies 
by the Bureau. Materials that are repetitively handled in 
the kneeling posture should not exceed 45 lb. Since the 
lifting tasks cannot be eliminated or mechanized by this 
mine, the weight of the rock dust bags needs to be reduced 
to conform to the reduced lifting capacity of miners in the 
kneeling posture. Therefore, the supplier of rock dust 
should be contacted and instructed to supply the rock dust 
in 40-lb bags, instead of the current 50-lb containers, so 
that the load does not exceed the recommended weight of 
lift for the kneeling posture. Other repetitively handled 
materials should also be redesigned to conform to the 
lifting capacity of underground miners in restricted pos- 
tures. Redesigning materials in this way has been shown 
to be an effective method of reducing the costs and in- 
cidence of back injuries (28). 



WORKER SELECTION AND TRAINING 
PROCEDURES 

Worker Selection 

While most jobs can be redesigned through one of the 
three approaches described above, occasionally such re- 
design may not be possible. Consider the following ex- 
ample. A low-seam mine requires the building of perma- 
nent ventilation stoppings using solid concrete block, 
weighing about 65 lb. Obviously, the need to build these 
stoppings means that the job cannot be eliminated. Be- 
cause of the complex nature of the lifting task, no suitable 
means of mechanizing this task is currently available. The 
mine has contacted the supplier and requested that the 
solid concrete block be reduced in weight to 45 lb (the 
acceptable weight limit for repetitively handled materials 
in the kneeling posture), but the supplier will not be able 
to supply the lighter blocks in the near future. In this 
example, the three preferred methods of redesigning the 
task cannot be used. In this case, it may be useful to 
select the worker who may be more apt to withstand the 
stresses of the job and who would therefore be at a lower 
risk of injury. 

Any test used to determine a worker's suitability for a 
job must be related to the specific demands of the job . (A 
task analysis can be used to ascertain the demands of a 
job.) If the test does not meet this criterion, then the 
selection procedure may be viewed as discriminatory, and 
legal action may result (32- 33). In addition to relating to 
the specific demands of the job, the test should be safe, 
should produce reliable results, should be practical to 
administer, and should be able to provide a reasonable 
prediction of future injury or illness (32-33). 

Since strength is an important factor in the ability to 
perform manual lifting tasks, a static strength test would 
be a reasonable test on which to base a decision as to 
which workers would be at less risk of injury in con- 
structing the permanent ventilation stopping. Therefore, 
the mine arranged to have tests done of the lifting strength 
of five of its laborers in a kneeling posture. Test results 
showed that Frank's lifting strength was 170 lb, Bob's was 
162 lb, Bill's was 150 lb, Ray's strength was 139 lb, and 
Mike's was 125 lb. The results indicate that Frank may be 
the best candidate for the job (less likely to become in- 
jured while building the solid-block ventilation stopping), 
because of his greater strength capability. If three workers 
are required for the task, Frank, Bob, Bill would be the 
recommended selections. The other workers should be 
assigned to chores that have been mechanized or designed 
not to exceed the recommended weight limits for repeti- 
tively handled materials (as described in the previous 
chapter). Proper worker selection procedures can be a 
useful tool in controlling the costs of back injuries in low- 
seam coal mines. A further discussion of worker selection 
and training criteria can be found in reference 33. 



27 



Worker Training 

While efforts to educate and train workers are an im- 
portant part of the overall safety strategy to reduce back 
injuries, this approach appears to be much less effective 
in reducing these injuries than the redesign approaches 
detailed previously. However, a thoughtfully designed 
training program can provide useful information and 
knowledge to the worker that can help minimize the risk 
of injury that may otherwise occur because of ignorance of 
certain fundamental concepts of manual lifting. The con- 
tents of such a course should include a basic understanding 
of the anatomy of the back, biomechanics of lifting, proper 
posture at work and at home, and physical fitness for back 
protection at work and at home, as well as simple concepts 
on psychological factors that may predispose a worker to 
injury (anxiety or stress on the job or at home, motivation, 
interactions on the job, etc.). The course should also 
provide hands-on experience in proper lifting techniques 
(32,34). 

In addition to the general training course contents de- 
scribed above, it may be useful to inform the workers of 
the results of the Bureau's lifting studies. For instance, 
miners should be made aware of the fact that lifting ca- 
pacity is significantly reduced in the kneeling posture as 
opposed to the stooped position. This means that if the 
worker has to lift a heavy object (>45 lbs), it may be better 
to handle the object in the stooped posture because of the 
increased lifting capacity in this posture. In addition, the 
Bureau studies have indicated that muscular fatigue occurs 
more quickly in the kneeling posture; thus, more frequent 
rest breaks should be taken in this posture. Providing 
specific information about the stresses of lifting in the 
restricted postures that low-seam miners have to use may 
help to reduce manual lifting injuries by increasing the 
worker's understanding of the limitations of lifting in these 
postures. 

IMPLEMENTATION AND EVALUATION 
OF REDESIGN STRATEGY 

Once a choice for the redesign of the task has been 
made, the new strategy must be put into effect. This step 
in the process often requires active communication among 
a number of individuals not influenced by the process until 



this point. Many of these individuals may play a very 
important role in whether the implementation of the strat- 
egy is successful (35). Though management might initiate 
a new method of performing a particular task, unless the 
idea is supported by the miners who must carry out the 
plan, implementation will be difficult. 

Evaluation of the newly implemented materials-handling 
strategy is another crucial step in the process of rede- 
signing the system. Occasionally, the strategy used to 
redesign a task may overlook important, unintended con- 
sequences. Therefore, it is crucial to get feedback on how 
the changes are working and how well the miners are 
accepting the new procedures (as well as soliciting sug- 
gestions from them on how the new plan might be made 
more effective). Unintended consequences are not always 
negative. For instance, a miner may fmd that a newly 
developed mechanical-assist device may work better for a 
lifting task other than the one for which it was originally 
developed. Nonetheless, providing the new mechanical- 
assist device will have been beneficial in reducing the 
number of times an object is manually lifted. Evaluation 
should consist of a systematized method of determining if 
the redesign strategy has fulfilled the desired goal of 
reducing the worker's risk of injury. 

SUMMARY 

This chapter has provided examples of several methods 
that can be used to redesign materials-handling tasks in 
low-seam coal mines to reduce the incidence and cost of 
musculoskeletal injuries. Many underground materials- 
handling tasks can be either eliminated or mechanized to 
reduce the number of manual lifts required in the supply- 
handling system. For tasks that cannot be eliminated or 
mechanized, the demands of the job can be matched to the 
worker's capabilities to perform the job. Occasionally, it 
may not be possible to use any of the three approaches 
mentioned above. In such cases, worker selection and 
training procedures may be the only methods that can be 
used to reduce the risk of worker injury. The examples 
in this chapter were provided to encourage mine manage- 
ment to evaluate current methods of handling supplies and 
to improve the supply system through the redesign strat- 
egies described. 



CHAPTER 5.-MANAGEMENT POLICY AND CONTROL OF BACK INJURY COSTS 



While the major focus of this report is that many jobs 
in low-seam coal mines can be ergonomically redesigned 
to reduce the risk of back injury, there are other ways that 
management can minimize the costs associated with these 
injuries. The first is to make a commitment to improving 
the physical fitness of the company's work force. The 
second deals with the way in which management responds 
when a back injury does occur. 



PROMOTION OF PHYSICAL FITNESS 

Mining can be a physically demanding job, which means 
that miners should be physically fit to meet the require- 
ments of the job. Unfortunately, research has shown that 
miners may actually be a bit less fit than other industrial 
workers (36). This indicates the importance of proper 
physical conditioning so that miners can better cope with 



28 



the demands of the job. Management support for pro- 
grams that help to keep the work force more physically fit 
may substantially reduce the costs associated with musculo- 
skeletal injuries. 

Back Fitness Program 

Low-seam coal miners spend a large portion of the 
working day in a posture that flexes the spine severely. 
Therefore, passive extension exercises (see the prone 
pushup below) to relieve the pressure experienced by the 
lumbar disks when the spine is flexed are recommended 
periodically throughout the workday. In addition, this 
program includes exercises to strengthen the abdominal 
muscles and the back extensor muscle group. The back 
fitness plan described below is a simple, effective method 
of caring for the back without spending much time in the 
process. However, such a program must be followed 
conscientiously to gain the maximum benefit. The worker 
should consult with a physician prior to participation in any 
exercise program! 

Step 1. Prone Pushup and Back Stretch 

Miners who work in low coal spend a large amount of 
time with their spines flexed, which creates a great deal of 
stress on the intervertebral disks, especially of the lumbar 
(low back) region. When the vertebral column is flexed, 
the jellylike material in the disk is moved toward the back 
of the disk, creating stress on the rear portion of the disk. 
Continued pressure on this region causes fibers of the disk 
to weaken and perhaps tear, thus leading to a back injury. 
Given the extreme amount of time spent in the flexed 
posture by underground miners, it is crucial that they 
perform exercises that put the vertebral column in exten- 
sion. Such exercises have the effect of relieving the pres- 
sure on the posterior (rear) portion of the disk and on the 
sensitive spinal nerve roots (27). 

By far the best exercise to achieve the goals stated 
above is the prone pushup. This exercise takes only a few 
minutes a day and yet can have a dramatic effect on the 
status of the low-back region. In fact, this exercise is often 
effective as the first treatment when the low back is in- 
jured. In addition, this exercise (as well as the other ex- 
ercises described below) can be performed in almost any 
low-seam coal mine. 

For the prone pushup (see figure 25A), lie flat on the 
stomach and, with the hands directly beneath the shoul- 
ders, push up while keeping the pelvis flat against the 
ground. Each pushup should be performed to the point 
of feeling a stretching or mild discomfort in the low back. 
A series of 10 pushups should be executed, followed by 
back stretches. The back stretches are performed by lying 
on the back and raising the left knee to the chest, then 
switching legs and raising the right knee to the chest, and 
finally raising both knees to the chest (fig. 255). These 



back stretches should be followed by another series of 10 
prone pushups (fig. 25C). This procedure should be per- 
formed two to four times a day. 

Step 2. Strengthening the Abdominal Muscle Group 

Strong abdominal muscles are also important in keeping 
a back healthy. However, the traditional exercise recom- 
mended for strengthening the abdominals (situps) can 
actually be quite harmful to the back. A much better 
alternative is the half situp, shown in figure 244. This 
exercise has the desired effect of increasing abdominal 
strength without loading the back to the extent that tra- 
ditional situps do. This exercise should be performed 
3 times a week with at least 20 half situps per session. 
The oblique abdominal muscles are best strengthened by 
the bicycle exercise shown in figure 265. Each leg should 
execute at least 30 repetitions, and legs should be 
alternated during this exercise. This exercise should be 
performed three times per week; however, it should not be 
performed if low back pain is currently being experienced. 

Step 3. Strengthening the Back Muscles 

Strengthening the back muscles is also recommended 
for underground miners. Increasing the strength of the 
back extensor muscles gives them an added reserve to rely 
upon when performing stressful manual materials-handling 
activities in restricted postures. A simple, yet effective, 
exercise is shown in figure 27. In this exercise, he flat on 
the stomach, interlock hands behind the head, and arch the 
back as far as possible for a count of 10. This exercise 
should be repeated five times during a session (one session 
per day). However, this exercise should not be performed 
if low-back pain is currently being experienced. 

Adherence to the simple exercise program outlined 
above may significantly reduce the cost and incidence of 
back pain in the underground mining industry. This back 
program would take only a few minutes out of the work- 
day, and management is encouraged to consider instituting 
such a program that would be performed by the miners 
during the workday. 

Stretching 

Probably the most important (and most neglected) 
action that can be taken to reduce the risk of overexertion 
injuries is to properly warm up before physically 
demanding tasks. Muscles that are "cold" (unstretched) 
are much more likely to be injured than those that have 
been properly prepared for activity through stretching. 
Stretching allows a muscle to receive more blood and 
oxygen and literally warms up the muscle. This allows the 
muscle to become more resistant to injury and actually 
increases the strength that can be produced by the muscle 
(37-38). 



29 





B 








Figure 25.-Prone pushup and back stretch. A, Begin with 10 prone pushups; 8, follow with 3 sets of knee-to-chest stretches; 
C, finish with 10 more prone pushups. 




Figure 26 -Abdominal strengthening exercises; these should 
be performed three times weekly. A, Half situp; B, horizontal 
bicycle. 



Figure 27.-Strengthening back muscles. (From "Oh, My 
Aching Back," by L Root and T. Kiernan, 1975; reprinted by 
permission of David McKay Co., a division of Random House, 
Inc.) 



30 



Strength Conditioning 

Strength conditioning, another method that can reduce 
the risk of injury, involves strengthening the muscles and 
joints through weight training. However, care should be 
taken to follow safe weight-training procedures, because 
improper weight training can be more hazardous than no 
training at all. Some mine operators have provided ex- 
ercise and weight-lifting equipment for use by their miners. 
This is an excellent method of helping to keep the work 
force in better condition so that they are better able to 
cope with the stresses of working underground. 

Back Care at Home 

Management should also emphasize that back care 
should not stop at the minesite. Many back injuries may 
be caused by everyday activities such as driving with the 
car seat too far back, doing yard work, or sleeping on a 
mattress that is too soft. There are also two-person lifting 
tasks at home. The safe lifting techniques employed at 
work should be transferred to the home environment. 

CONTROL OF COSTS ONCE A BACK 
INJURY HAS OCCURRED 

The previous sections have detailed methods that can 
be useful in preventing low-back injuries. However, it is 
important for management to realize that some back in- 
juries probably will occur, despite efforts to prevent them. 
When back injuries do occur, the policy that management 
puts in place to deal with the injury may be significant in 
determining the duration of the disability and the costs 
incurred by the company. 

As discussed in a paper entitled "The Control of Low 
Back Disability: The Role of Management" by Snook (39), 
management often does not respond properly when a 
worker experiences a back injury. The injured worker may 
be accused of malingering either by direct accusation or 
through innuendo. This, in turn, causes the worker to look 
for ways to get back at management. As such adversary 
situations develop, the costs of the injury may significantly 
increase for both the worker and management. However, 
as discussed by Snook (39), studies have indicated that 
enlightened management can often reduce and perhaps 
even prevent the disability associated with back injuries 
through a program that includes positive acceptance of 
low-back pain, early intervention, good communication and 
followup, and early return-to-work programs. 

Positive Acceptance of Low-Back 
Pain by Management 

The most appropriate response by a supervisor to a 
back injury experienced by one of his or her workers is to 
show concern for the needs of the employee and to avoid 
making rash judgments and setting up adversary relation- 
ships because of the injury. Such judgments are usually 
incorrect and may serve to make the situation worse than 



it should be. Instead, management should be trained to 
realize that a certain number of back injuries are likely to 
occur and should be taught to respond in an appropriate 
manner when they do occur. The supervisor should en- 
courage the worker to seek immediate medical treatment 
and (if possible) adapt the workplace or modify the task 
so that the employee can continue to work on the job. 
One company that instituted a policy of positive acceptance 
of low-back pain immediately and dramatically reduced 
their worker compensation costs. Over a 3-year period, 
costs were reduced from over $200,000 per year to about 
$20,000 per year (39). 

Early Intervention 

One key feature of the program described above was 
that all workers complaining about low-back pain were 
immediately referred to the company clinic for treatment- 
even those with minor complaints. Treatment was given 
during work time by the company nurse. This treatment 
consisted of heat applications and nonprescription anal- 
gesic or anti-inflammatory drugs such as aspirin. During 
the treatment sessions, worker education was initiated on 
a one-to-one basis. The education program consisted of 
basic spinal anatomy and physiology, the expected results 
from the treatment regimen, proper posture, and suitable 
exercises. Light-duty work and rest periods were provided 
by management to the injured employee. If the initial in- 
house treatment was ineffective, the worker was referred 
to the company physician for further medical treatment. 
The physicians were familiarized with the physical de- 
mands of the jobs at the company in order to place injured 
workers in appropriate job positions. 

Because this company encouraged the reporting of all 
episodes of low-back pain (even minor cases), it is not 
surprising that the number of cases reported actually in- 
creased. However, the amount of lost time due to back 
injuries was significantly reduced. This indicates that the 
workers were able to stay on the job and did not rely on 
outside practitioners for treatment, thus reducing the 
company's cost due to low-back pain. 

Followup and Communication 

When workers do become temporarily disabled, it is 
important that management establish and maintain good 
communications with the worker and appropriate medical 
personnel. Supervisors should be instructed to follow up 
every disability case with a telephone call or visit before 
2 days of lost time have elapsed. The purpose of the call 
is to let the worker know that the company is concerned 
and to inform the supervisor of the status of the worker's 
recovery. 

One company recently instituted a program that in- 
creased the communication between the worker, employer, 
medical practitioner, and insurer (39). When a worker 
compensation claim was received, the employer made 
immediate contact with the worker and insurer and fol- 
lowed up with calls at regular 10-day intervals to make 



31 



certain that the claim was progressing smoothly. The 
possibility of retraining was explored for extended claims, 
and a liaison was established between management and the 
insurer if a gradual return to work was indicated. The 
focus of all communications was that every action taken 
was in the best interest of the worker. This program sig- 
nificantly reduced the proportion of long-term worker 
compensation claims and also significantly reversed a trend 
of increasing accident rates (39). 

Early Return-to-Work Programs 

The data from several studies have shown that the 
longer a worker is off from work because of a back injury, 
the less likely the worker will return to productive em- 
ployment. These studies underscore the importance of 
providing modified, alternative, or part-time work to the 
injured employee to facilitate a quick return to the job. 
Unfortunately, management often extends the period of 
disability by requiring workers to be fully recovered before 
returning to work, which can be a costly policy. Because 
there appears to be a limited amount of time to act be- 
fore losing control of the disability and the claim, effi- 
cient management should do everything in its power to 



encourage the worker's timely return to work. Data 
indicate that an early return to work is in the best interests 
of everyone: the worker, the company, and the union. In 
this regard, it may benefit both the company and the union 
to ensure that work rules in the current contract do not 
interfere with early return-to-work programs. 

SUMMARY 

A common complaint of management is that the high 
costs of back injuries are the result of dissatisfied workers, 
ineffective medical personnel, and activist unions. How- 
ever, management must also share in the responsibility 
when it does not respond appropriately to low-back in- 
juries. The examples cited above indicate that there is a 
substantial amount that management can do to control the 
high costs associated with back injuries through improving 
worker fitness, positive acceptance of low-back pain, early 
intervention measures, improved followup and communi- 
cation procedures, and early return-to-work programs. 
Back injuries may not be entirely preventable at the pres- 
ent time, but there is evidence that management can ef- 
fectively reduce the costs associated with low-back injuries. 



CHAPTER 6.-SUMMARY OF RECOMMENDATIONS 



This report has described methods that may be used to 
reduce the costs and incidence of back injuries in low-seam 
coal mines. The primary intent of the report was to dem- 
onstrate that workers' risk of experiencing back injuries 
and other musculoskeletal injuries can be reduced through 
ergonomic redesign of underground materials-handling 
tasks. These methods have been successful in reducing 
injury costs in other industries, and if correctly imple- 
mented, they can do the same in underground coal mines. 
Several examples of successful redesign strategies have 
been provided. The model illustrated in figure 1 has been 
presented as a guideline that can be used in evaluating and 
improving current materials-handling practices in low-seam 
coal mines. This chapter briefly reviews the procedure for 
redesigning materials-handling tasks as outlined in fig- 
ure 1. 

The first step in improving a mine supply-handling 
system is to examine the current materials-handling prac- 
tices in detail (see figure 2). Dependable data need to be 
collected that identify both favorable and inappropriate 
supply-handling strategies currently being used at the 
minesite. For redesign purposes, it is necessary to focus 
on identification of materials-handling problem areas in 
the current system. Two techniques that can be used in 
this effort are accident analysis and task analysis. A review 
of past accident records can provide a great deal of insight 
on current supply-handling problems. Hazardous occupa- 
tions or tasks can be identified as candidates for job 
redesign using the techniques described in this report. A 
task analysis can then be used to document and analyze 
current work practices, so that appropriate job or task 



redesign can be performed to minimize injury risk to the 
worker. Videotape is a particularly useful tool for task 
analysis, as the analyst can view the worker performing the 
job in "real" time. A particular concern of the analyst is to 
minimize the number of times materials (especially heavy 
materials) have to be manually lifted. Greater detail on 
accident and task analysis is found in chapter 1. 

Chapters 2 and 3 of this report describe alternative 
strategies that can be used to more safely handle materi- 
als in low-seam coal mines. To the extent possible, jobs 
should be redesigned with an emphasis on constructing an 
efficient and integrated materials-handling system; in other 
words, a systems approach to materials-handling should be 
developed. The benefits of instituting a systems approach 
may include improved coordination with suppliers, fewer 
delays in mine operation, higher equipment utilization, 
better scheduling, fewer materials lost because of break- 
age, and safer, more systematic work procedures. 

The two best redesign alternatives for manual materials- 
handling chores are task elimination and using a 
mechanical-assist device to perform the task. These meth- 
ods significantly reduce the number of times materials are 
manually lifted and thus provide the greatest potential for 
preventing musculoskeletal injuries. Careful examination 
of the current supply-handling system will probably identify 
several tasks that can be eliminated, reduced, or combined 
to improve the flow of supplies. Eliminating unnecessary 
tasks not only improves efficiency and economy of the 
system, it also greatly reduces the risk of worker injury by 
reducing their exposure to hazardous lifting conditions. 



32 



If task elimination is not possible, the next best redesign 
solution is to have a mechanical-assist device perform the 
lifting task. With good planning, it is often possible to 
handle supplies almost entirely through mechanical means. 
A common flaw in supply systems of many mines is that 
supplies are delivered on pallets or in unit loads only to be 
broken apart on the surface, necessitating considerable 
manual lifting. One problem experienced in low-seam coal 
mines is that traditional mechanical-assist devices (such as 
forklifts, cranes, or hoists) cannot be used because of the 
restrictive roof height. However, Bureau research has 
demonstrated that task-specific mechanical assists can be 
developed at fairly low expense. Many such devices (which 
are described in chapter 2) can be fabricated in a well- 
equipped mine shop. 

Unfortunately, not all materials-handling tasks can be 
eliminated or mechanized. When manual lifting is neces- 
sary, the lifting task should be designed so that the work- 
er's physical capabilities are not exceeded. Recent Bureau 
research has shown that the postures that low-seam coal 
miners must adopt to perform lifting tasks may signif- 
icantly limit the amount of weight that can be safely lifted. 
For instance, in a kneeling posture, a miner's lifting ca- 
pacity is approximately 18 pet lower than in a stooping 
posture. Data from Bureau lifting capacity studies indicate 
that for compact, repetitively handled loads (such as rock 
dust bags, ventilation stopping blocks, and crib blocks), 
55 lb is the maximum recommended weight in the stooped 
posture and 45 lb is the maximum recommended weight in 
the kneeling posture. Because all low-seam mines require 
significant periods of lifting in kneeling posture, it is sug- 
gested that supplies be designed in accordance with the 
reduced lifting capacity of miners in the kneeling posture. 
Additional recommendations for manual lifting in low- 
seam mines are provided in chapter 3. 

While the three redesign strategies described above will 
probably have the greatest impact in reducingHhe threat of 
worker injury, other methods can be used to reduce injury 
risk. These techniques include worker selection and work- 
er training. Worker selection usually includes evaluation 
of one or more of the following: physical strength, aerobic 
capacity, or a clinical evaluation of the individual. The test 
or tests administered need to be directly related to the 
demands of the job to prevent accusations of discrimi- 
natory selection procedures (32-33). Worker training may 
be considered if none of the previous methods can be 
used. Unfortunately, training does not appear to be as 
effective in controlling injuries as those described earlier. 
A training program on manual lifting should include the 
following topics: risks of unsafe materials handling, basic 
anatomy and biomechanics of lifting, use of mechanical- 
assist devices, and accident avoidance. Active involvement 
of the worker is crucial to the success of the program (34). 
These injury control methods are described in greater 
detail in chapter 4. 



Once the appropriate redesign strategy has been cho- 
sen, the new strategy must be implemented. This step 
may be the most important determinant of the success of 
the redesign program. Many redesign strategies may fail, 
not because of a flawed concept, but because of poor 
implementation practices. The new strategy may be devel- 
oped by management, but it is the miners who ultimately 
determine how well the new plan will work. If the miners 
are hostile toward the redesign strategy, proper implemen- 
tation of the plan will be difficult. Active communication 
between management and labor is an important consider- 
ation during this phase and will improve the chances of 
successful implementation of the new work practices. 

Evaluation of the newly developed materials-handling 
strategy is another crucial step in the process of rede- 
signing the system. Occasionally, the strategy put into 
effect may overlook important, unintended consequences. 
It is not unusual for a strategy to have an effect that was 
not calculated or anticipated, though these effects may not 
always be negative (35). Therefore, it is crucial to get 
feedback on how well the changes are working and how 
well the miners are accepting the new procedures. The 
evaluation phase should not only address how well the 
procedure has reduced injury risk but also consider how 
the new strategy has affected other aspects of the working 
environment. Implementation and evaluation of the rede- 
sign strategy are discussed in chapter 4. 

Management must realize that not all back injuries 
will be preventable. However, a policy that encourages a 
prompt return to the workplace is sure to have a large 
positive influence on worker welfare and on the costs 
incurred by the company. Enlightened management can 
reduce or even prevent disability associated with back 
injuries through a policy that includes positive acceptance 
of low-back pain, early intervention strategies, good com- 
munication and followup procedures, and early return-to- 
work programs (39). Details of such a policy are de- 
scribed in chapter 5. 

Compared with most industrial settings, low-seam coal 
mines present relatively unique barriers to using proper 
lifting techniques or achieving mechanical transfer of ma- 
terials. However, the rapid emergence and continued 
development of the field of ergonomics provides mines 
with new and innovative solutions that can be used to 
reduce the costs and incidence of back injuries. Risk of 
back injury can be reduced through proper design of jobs 
and matching the job demands to the capabilities of the 
underground worker. This report has recommended prac- 
tices for handling materials in low-seam coal mines. 
Methods have been provided to examine and redesign 
current supply-handling systems to reduce the threat of 
back injury. The strategies contained in this report, if 
correctly implemented, can significantly reduce the cost 
and incidence of materials-handling injuries in low-seam 
coal mines. 



33 



REFERENCES 



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37. Krejci, V., and P. Koch. Muscle and Tendon Injuries in Athletes. 
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pp. 97-102. 



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